2,320 results on '"Range (particle radiation)"'
Search Results
2. Absorption spectrum of neutral krypton in the near infrared region
- Author
-
Hailing Wang, Ruo-yu Jiang, Lunhua Deng, and Jia Ye
- Subjects
Range (particle radiation) ,Materials science ,Absorption spectroscopy ,Krypton ,Near-infrared spectroscopy ,chemistry.chemical_element ,Laser ,law.invention ,chemistry ,law ,Excited state ,Energy level ,Physical and Theoretical Chemistry ,Atomic physics ,Helium - Abstract
High-resolution absorption spectra of atomic krypton in the range of 11870-12700 cm $^{-1}$ were recorded by employing concentration modulation absorption spectroscopy technique with a tunable single-mode cw Ti:Sapphire laser. The krypton atoms were excited to the absorbing energy states by discharge-burning in a mixture of helium and krypton. A total of 120 lines of neutral krypton were observed, among them 33 lines had already been classified in previous studies, 45 lines were newly classified with the known energy levels, and 42 lines cannot be classified. These unclassified lines indicate that up to now unknown energy levels of Kr must exist. Further, an analysis of the unclassified lines to get possible new energy levels with a classification program is reported.
- Published
- 2019
3. Dynamics and phase behavior of two-dimensional size-asymmetric binary mixtures of core-softened colloids
- Author
-
Luis A Padilla, Julio C. Armas-Pérez, Andres A Leon-Islas, Abelardo Ramírez-Hernández, and Jesse Funkhouser
- Subjects
endocrine system ,Range (particle radiation) ,Materials science ,digestive, oral, and skin physiology ,Lattice (group) ,General Physics and Astronomy ,Binary number ,Electron ,complex mixtures ,body regions ,Condensed Matter::Soft Condensed Matter ,Colloid ,Chemical physics ,Phase (matter) ,Physical and Theoretical Chemistry ,Stoichiometry ,Phase diagram - Abstract
The self-assembly of binary colloidal mixtures provides a bottom-up approach to create novel functional materials. To elucidate the effect of composition, temperature and pressure on the self-assembly behavior of size-asymmetric mixtures, we performed extensive dynamics simulations of a simple model of polymer-grafted colloids. We have used a core-softened interaction potential and extended it to represent attractive interactions between unlike colloids and repulsion between like colloids. Our study focused on size-asymmetric mixtures, where the ratio between the sizes of the colloidal cores was fixed at $\frac{\sigma_{B}}{\sigma_{A}}=0.5$. We have performed extensive simulations in the NPT and NVT ensembles to elucidate the phase behavior and dynamics of mixtures with different stoichiometric ratios. Our simulation results uncovered a rich phase behavior, including the formation of hierarchical structures with many potential applications. For compositions where the small colloids are the majority, sublattice melting occurs for a wide range of densities. As the temperature is decreased, the small colloids localize, akin to a metal-insulator transition, with the small colloids playing a role similar to electrons. Under these conditions the large colloids form a well-defined lattice, whereas small colloids can diffuse through the system. Our results are summarized in terms of phase diagrams.
- Published
- 2021
4. Enhanced local viscosity around colloidal nanoparticles probed by equilibrium molecular dynamics simulations
- Author
-
Ali Rajabpour, Samy Merabia, Laurent Joly, Mohammad Hassan Saidi, Reza Rabani, Sharif University of Technology [Tehran] (SUT), Modélisation de la matière condensée et des interfaces (MMCI), Institut Lumière Matière [Villeurbanne] (ILM), Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Centre National de la Recherche Scientifique (CNRS)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Centre National de la Recherche Scientifique (CNRS), Institut Universitaire de France (IUF), Ministère de l'Education nationale, de l’Enseignement supérieur et de la Recherche (M.E.N.E.S.R.), and Imam Khomeini International University (IKIU)
- Subjects
Materials science ,Diffusion ,FOS: Physical sciences ,General Physics and Astronomy ,Nanoparticle ,02 engineering and technology ,Condensed Matter - Soft Condensed Matter ,Molecular dynamics ,010402 general chemistry ,01 natural sciences ,Slip (ceramics) ,Physics::Fluid Dynamics ,Metal ,[SPI]Engineering Sciences [physics] ,Viscosity ,Nanofluid ,Physical and Theoretical Chemistry ,Diffusion coefficient ,[PHYS]Physics [physics] ,Condensed Matter - Materials Science ,Range (particle radiation) ,Nanofluidics ,Materials Science (cond-mat.mtrl-sci) ,021001 nanoscience & nanotechnology ,0104 chemical sciences ,Chemical physics ,visual_art ,visual_art.visual_art_medium ,Nanoparticles ,Soft Condensed Matter (cond-mat.soft) ,0210 nano-technology - Abstract
Nanofluids-dispersions of nanometer-sized particles in a liquid medium-have been proposed for a wide variety of thermal management applications. It is known that a solid-like nanolayer of liquid of typical thicknesses of 0.5-1 nm surrounding the colloidal nanoparticles can act as a thermal bridge between the nanoparticle and the bulk liquid. Yet, its effect on the nanofluid viscosity has not been elucidated so far. In this article, we compute the local viscosity of the nanolayer using equilibrium molecular dynamics based on the Green-Kubo formula. We first assess the validity of the method to predict the viscosity locally. We apply this methodology to the calculation of the local viscosity in the immediate vicinity of a metallic nanoparticle for a wide range of solid-liquid interaction strength, where a nanolayer of thickness 1 nm is observed as a result of the interaction with the nanoparticle. The viscosity of the nanolayer, which is found to be higher than its corresponding bulk value, is directly dependent on the solid-liquid interaction strength. We discuss the origin of this viscosity enhancement and show that the liquid density increment alone cannot explain the values of the viscosity observed. Rather, we suggest that the solid-like structure of the distribution of the liquid atoms in the vicinity of the nanoparticle contributes to the nanolayer viscosity enhancement. Finally, we observe a failure of the Stokes-Einstein relation between viscosity and diffusion close to the wall, depending on the liquid-solid interaction strength, which we rationalize in terms of the hydrodynamic slip.
- Published
- 2021
5. Intensity dependence of multiply charged atomic ions from argon clusters in moderate nanosecond laser fields
- Author
-
Yuzhong Yao, Lan Xue, Rahul Pandey, Di Wu, Wei Kong, and Jie Zhang
- Subjects
Range (particle radiation) ,Materials science ,Argon ,Field (physics) ,General Physics and Astronomy ,chemistry.chemical_element ,02 engineering and technology ,021001 nanoscience & nanotechnology ,Kinetic energy ,Laser ,01 natural sciences ,Ion ,law.invention ,chemistry ,law ,Ionization ,0103 physical sciences ,Mass spectrum ,Physics::Atomic Physics ,Physical and Theoretical Chemistry ,Atomic physics ,010306 general physics ,0210 nano-technology - Abstract
We report the laser intensity dependence of multiply charged atomic ions (MCAIs) Arn+ with 2 ≤ n ≤ 8 from argon clusters in focused nanosecond laser fields at 532 nm. The laser field, in the range of 1011–1012 W/cm2, is insufficient for optical field ionization but is adequate for multiphoton ionization. The MCAI sections of the mass spectra for clusters containing 3700 and 26 000 atoms are dominated by Arn+ with 7 ≤ n ≤ 9, extending to Ar14+. While the distributions of the MCAIs remain largely constant throughout the intensity range of the laser, the abundance of Ar+ relative to the abundances of the MCAIs increases dramatically with increasing laser intensity. Consequently, exponential fittings of the yields result in a larger exponent for Ar+ than for MCAIs, and the exponents of MCAIs with 2 ≤ n ≤ 8 are similar, with only slight variations for different charge states. The width of the arrival time and, hence, the corresponding kinetic energy of Ar+ also increases with increasing laser intensities, while the width of the arrival time of MCAIs remains constant throughout the range of measurements. These results call for more detailed theoretical investigations in this regime of laser–matter interactions.
- Published
- 2021
6. Aggregation of discoidal particles due to depletion interaction
- Author
-
M. Díaz-Morata, Carles Calero, and Ignacio Pagonabarraga
- Subjects
Col·loides ,Range (particle radiation) ,Materials science ,Thermodynamic equilibrium ,General Physics and Astronomy ,Partícules (Matèria) ,Aggregation (Chemistry) ,Condensed Matter::Soft Condensed Matter ,Thermodynamic model ,molecular-dynamics simulations ,Colloid ,Particles ,mixtures ,Rheology ,Chemical physics ,Agregació (Química) ,Colloids ,Physical and Theoretical Chemistry ,force - Abstract
Depletion interactions between colloids of discoidal shape can induce their self-assembly into columnar aggregates. This is an effect of entropic origin with important implications in a range of colloidal systems, particularly in the clustering of erythrocytes that determine the rheological properties of blood. Here, we investigate the equilibrium state reached by discoidal colloids in a solution of smaller depletant particles. We develop a thermodynamic model of depletion-induced aggregation based on self-assembly theory and solve it analytically. We test the validity of the model by using Langevin simulations of a system of discs and depletant particles in which the depletion interaction emerges naturally. In addition, we consider the effect of an attractive interaction between depletant and discoidal particles, which we show induces a re-entrant dependence of aggregation with temperature.
- Published
- 2021
7. Electron ratcheting in self-assembled soft matter
- Author
-
David N. Beratan, Jesús Valdiviezo, and Peng Zhang
- Subjects
education.field_of_study ,Range (particle radiation) ,Materials science ,Static Electricity ,Population ,Electric Conductivity ,General Physics and Astronomy ,Charge (physics) ,DNA ,Electron ,Molecular physics ,Nanostructures ,Kinetics ,Electric field ,Electrochemistry ,Soft matter ,Physical and Theoretical Chemistry ,education ,Nanoscopic scale ,Voltage - Abstract
Ratcheted multi-step hopping electron transfer systems can plausibly produce directional charge transport over very large distances without requiring a source–drain voltage bias. We examine molecular strategies to realize ratcheted charge transport based on multi-step charge hopping, and we illustrate two ratcheting mechanisms with examples based on DNA structures. The charge transport times and currents that may be generated in these assemblies are also estimated using kinetic simulations. The first ratcheting mechanism described for nanoscale systems requires local electric fields on the 109 V/m scale to realize nearly 100% population transport. The second ratcheting mechanism for even larger systems, based on electrochemical gating, is estimated to generate currents as large as 0.1 pA for DNA structures that are a few μm in length with a gate voltage of about 5 V, a magnitude comparable to currents measured in DNA wires at the nanoscale when a source–drain voltage bias of similar magnitude is applied, suggesting an approach to considerably extend the distance range over which DNA charge transport devices may operate.
- Published
- 2021
8. Interfacial stiffness of nematic–smectic B interface in Gay–Berne liquid crystals using capillary wave theory
- Author
-
Jagroop Kaur and Debabrata Deb
- Subjects
Range (particle radiation) ,Capillary wave ,Molecular dynamics ,Materials science ,Condensed matter physics ,Liquid crystal ,Phase (matter) ,Perpendicular ,General Physics and Astronomy ,Physical and Theoretical Chemistry ,Pair potential ,Bond order - Abstract
The interfacial stiffness for nematic–smectic B (nm–smB) interface in a liquid crystalline (LC) material is calculated using Capillary Wave Theory (CWT) and molecular dynamics simulations. The Gay–Berne (GB) pair potential with parameters κ, κ′, μ, and ν equal to 3, 5, 2, and 1 is used to model the LC material. Using a smart three-step recipe, we have obtained an nm–smB phase coexistence in our simulations where the nm and smB directors are nearly parallel to each other and perpendicular to the interface normal. The density profiles are used to compute the nm–smB coexisting density range, the interfacial width, and its position. The smectic phase is differentiated from the nematic phase by using the local bond order parameter (q6q6), which has helped us to demonstrate that the interface is indeed rough. Finally, the interfacial stiffness of the nm–smB interface is computed by following the CWT analysis and is found to be γnm−smB=0.39861kBT/σee2=0.04429/σss2, where σee and σss are the length and diameter of the GB LC particles.
- Published
- 2021
9. Structure, energy, and bonding in anionic water tetramers obtained by exhaustive search
- Author
-
Albeiro Restrepo, C. Z. Hadad, and Norberto Moreno
- Subjects
Crystallography ,Range (particle radiation) ,Materials science ,Hydrogen bond ,Potential energy surface ,General Physics and Astronomy ,Molecule ,Electron ,Physical and Theoretical Chemistry ,Some Energy ,Ground state ,Open shell - Abstract
An analysis of the structures, some energy related properties, and key aspects of the bonding nature of the microsolvated electron with four water molecules is presented. The study is based on an exhaustive potential energy surface scan of the ground state of (H2O)4− at the UCCSD(T)/6-311(3+,4+)G(d,p)//UMP2/6-311(3+,4+)G(d,p) level. A total of 18 structures, most of them not reported before, spanning in an energy range of 8.8 kcal mol−1 were found. The energetic stability of the clusters is dictated by the effect of the excess electron on their structures, on their partial fragmentation, and on the hydrogen bonds’ framework. Vertical detachment energies depend on the number of water molecules holding the excess electron in “direct contact” to their two protons at the same time and, to a lesser extent, also depend on the hydrogen bond sequence in the rest of the structure. In general, hydrogen bonds in (H2O)4− are of closed shell character, and there are other less common interactions assisted by the excess electron.
- Published
- 2021
10. Fragmentation of propionitrile (CH3CH2CN) by low energy electrons
- Author
-
A. Ribar Valah, K. Marciszuk, Stephan Denifl, Andrzej Pelc, and Stefan E. Huber
- Subjects
Range (particle radiation) ,010304 chemical physics ,Chemistry ,Radical ,General Physics and Astronomy ,Electron ,010402 general chemistry ,Photochemistry ,01 natural sciences ,0104 chemical sciences ,Ion ,chemistry.chemical_compound ,Fragmentation (mass spectrometry) ,0103 physical sciences ,Molecule ,Dehydrogenation ,Propionitrile ,Physical and Theoretical Chemistry - Abstract
Propionitrile (CH3CH2CN, PN) is a molecule relevant for interstellar chemistry. There is credible evidence that anions, molecules, and radicals that may originate from PN could also be involved in the formation of more complex organic compounds. In the present investigation, dissociative electron attachment to CH3CH2CN has been studied in a crossed electron–molecular beam experiment in the electron energy range of about 0–15 eV. In the experiment, seven anionic species were detected: C3H4N−, C3H3N−, C3H2N−, C2H2N−, C2HN−, C2N−, and CN−. The anion formation is most efficient for CN− and anions originating from the dehydrogenation of the parent molecule. A discussion of possible reaction channels for all measured negative ions is provided. The experimental results are compared with calculations of thermochemical thresholds of the detected anions.
- Published
- 2021
11. Monodisperse patchy particle glass former
- Author
-
Frank Smallenburg, Francesco Sciortino, Susana Marín-Aguilar, Giuseppe Foffi, Laboratoire de Physique des Solides (LPS), Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS), Dipartimento di Fisica [Roma La Sapienza], and Università degli Studi di Roma 'La Sapienza' = Sapienza University [Rome]
- Subjects
glass transition, patchy particles, molecular dynamics ,Materials science ,Icosahedral symmetry ,Dispersity ,General Physics and Astronomy ,010402 general chemistry ,Condensed Matter::Disordered Systems and Neural Networks ,01 natural sciences ,Local structure ,law.invention ,law ,0103 physical sciences ,glass transition ,Physical and Theoretical Chemistry ,Crystallization ,ComputingMilieux_MISCELLANEOUS ,patchy particles ,Range (particle radiation) ,010304 chemical physics ,molecular dynamics ,0104 chemical sciences ,Condensed Matter::Soft Condensed Matter ,Chemical physics ,Particle ,Patchy particles ,[PHYS.COND.CM-SCM]Physics [physics]/Condensed Matter [cond-mat]/Soft Condensed Matter [cond-mat.soft] - Abstract
Glass formers are characterized by their ability to avoid crystallization. As monodisperse systems tend to rapidly crystallize, the most common glass formers in simulations are systems composed of mixtures of particles with different sizes. Here, we make use of the ability of patchy particles to change their local structure to propose them as monodisperse glass formers. We explore monodisperse systems with two patch geometries: a 12-patch geometry that enhances the formation of icosahedral clusters and an 8-patch geometry that does not appear to strongly favor any particular local structure. We show that both geometries avoid crystallization and present glassy features at low temperatures. However, the 8-patch geometry better preserves the structure of a simple liquid at a wide range of temperatures and packing fractions, making it a good candidate for a monodisperse glass former.
- Published
- 2021
12. Maximal kinetic energy and angular distribution analysis of spatial map imaging: Application to photoelectrons from a single quantum state of H2O
- Author
-
Yair Yifrach, Alexander Portnov, Rami Rahimi, Ilana Bar, and Joshua H. Baraban
- Subjects
Physics ,Range (particle radiation) ,010304 chemical physics ,Detector ,General Physics and Astronomy ,Photoelectric effect ,010402 general chemistry ,Kinetic energy ,01 natural sciences ,Charged particle ,0104 chemical sciences ,Computational physics ,Acceleration ,0103 physical sciences ,Physical and Theoretical Chemistry ,Anisotropy ,Electrostatic lens - Abstract
Dynamical or spatial properties of charged species can be obtained using electrostatic lenses by velocity map imaging (VMI) or spatial map imaging (SMI), respectively. Here, we report an approach for extracting dynamical and spatial information from patterns in SMI images that map the initial coordinates, velocity vectors, and angular distributions of charged particles onto the detector, using the same apparatus as in VMI. Deciphering these patterns required analysis and modeling, involving both their predictions from convolved spatial and velocity distributions and fitting observed images to kinetic energies (KEs) and anisotropy parameters (βs). As the first demonstration of this capability of SMI, the ensuing photoelectrons resulting from (2 + 1) resonant ionization of water in a selected rotational state were chosen to provide a rigorous basis for comparison to VMI. Operation with low acceleration voltages led to a measured SMI pattern with a unique vertical intensity profile that could be least-squares fitted to yield KE and β, in good agreement with VMI measurement. Due to the potential for improved resolution and the extended KE range achievable by this new technique, we expect that it might augment VMI in applications that require the analysis of charged particles and particularly in processes with high KE release.
- Published
- 2021
13. Theoretical Simulations of Irradiation-Induced Sputtering at Tungsten Surface
- Author
-
Bicai Pan, Xuemin Hua, Junling Chen, Wenyi Ding, Haiyan He, and Ru Ding
- Subjects
010302 applied physics ,Surface (mathematics) ,Range (particle radiation) ,Materials science ,chemistry.chemical_element ,Tungsten ,01 natural sciences ,010305 fluids & plasmas ,Molecular dynamics ,chemistry ,Sputtering ,0103 physical sciences ,Atom ,Irradiation ,Physical and Theoretical Chemistry ,Atomic physics ,Plasma-facing material - Abstract
The irradiation-induced sputtering and the structural damage at tungsten surface are investigated by using molecular dynamics simulations at the level of quantum mechanics. Our simulations indicate that the sputtered atoms appear when the energy of incident primary knock-on atom (PKA) is more than 200 eV and the incident angle of the PKA is larger than 65°. Meanwhile, the irradiation-induced vacancies are less when the incident angle of PKA is in the range of 45°–65°. So, the optimum incident angles of PKA are suggested to reduce the irradiation-induced damage of the W surface. Furthermore, we find that the interstitials contained in the systems accelerate the sputtering whereas the intrinsic vacancies suppress the sputtering when the PKA is near the defects.
- Published
- 2017
14. Macroscopic relations for microscopic properties at the interface between solid substrates and dense fluids
- Author
-
Miguel A. Durán-Olivencia, Antonio Russo, Remco Hartkamp, and Serafim Kalliadasis
- Subjects
Fluid viscosity ,Range (particle radiation) ,State variable ,Materials science ,Chemical Physics ,02 Physical Sciences ,Interface (Java) ,General Physics and Astronomy ,Interaction strength ,Nanofluidics ,Tribology ,09 Engineering ,Physics::Fluid Dynamics ,Viscosity ,Chemical physics ,Physical and Theoretical Chemistry ,03 Chemical Sciences - Abstract
Strongly confined fluids exhibit inhomogeneous properties due to atomistic structuring in close proximity to a solid surface. State variables and transport coefficients at a solid-fluid interface vary locally and become dependent on the properties of the confining walls. However, the precise mechanisms for these effects are not known as of yet. Here, we make use of nonequilibrium molecular dynamics simulations to scrutinize the local fluid properties at the solid-fluid interface for a range of surface conditions and temperatures. We also derive microscopic relations connecting fluid viscosity and density profiles for dense fluids. Moreover, we propose empirical ready-to-use relations to express the average density and viscosity in the channel as a function of temperature, wall interaction strength, and bulk density or viscosity. Such relations are key to technological applications such as micro-/nanofluidics and tribology but also natural phenomena.
- Published
- 2019
15. Signature of shape resonances on the differential cross sections of the S(1D)+H2 reaction
- Author
-
F. J. Aoiz, Manuel Lara, and Pablo G. Jambrina
- Subjects
Excitation function ,Physics ,Work (thermodynamics) ,Range (particle radiation) ,010304 chemical physics ,Scattering ,General Physics and Astronomy ,Resonance ,010402 general chemistry ,01 natural sciences ,Molecular physics ,Helicity ,0104 chemical sciences ,Cross section (physics) ,0103 physical sciences ,Physical and Theoretical Chemistry ,Quantum tunnelling - Abstract
Shape resonances appear when the system is trapped in an internuclear potential well after tunneling through a barrier. They manifest as peaks in the collision energy dependence of the cross section (excitation function), and in many cases, their presence can be observed experimentally. High-resolution crossed-beam experiments on the S(1D) + H2(j = 0) reaction in the 0.81–8.5 meV collision energy range reaction revealed non-monotonic behavior and the presence of oscillations in the reaction cross section as a function of the collision energy, as predicted by quantum mechanical (QM) calculations. In this work, we have analyzed the effect of shape resonances on the differential cross sections for this insertion reaction by performing additional QM calculations. We have found that, in some cases, the resonance gives rise to a large enhancement of extreme backward scattering for specific final states. Our results also show that, in order to yield a significant change in the state-resolved differential cross section, the resonance has to be associated with constructive interference between groups of partial waves, which requires not getting blurred by the participation of many product helicity states.
- Published
- 2021
16. Direct time delay computation applied to the O + O2 exchange reaction at low energy: Lifetime spectrum of O3* species
- Author
-
Grégoire Guillon, Pascal Honvault, and Erwan Privat
- Subjects
Physics ,Range (particle radiation) ,Total angular momentum quantum number ,Scattering ,Metastability ,Spectrum (functional analysis) ,Domain (ring theory) ,Zero (complex analysis) ,General Physics and Astronomy ,Physical and Theoretical Chemistry ,Atomic physics ,Quantum - Abstract
We report full quantum dynamical calculations for lifetimes of scattering resonances, among which are true metastable states, of the intermediate heavy ozone complex 50O3* of the 18O + 16O16O reaction, for any value of the total angular momentum quantum number J. We show that computations for nonzero values of J are mandatory in order to properly analyze resonances and time delays, with a view to establish a somewhat comprehensive eigenlife spectrum of the complex O3*. Calculations have been performed in a given low to moderate energy range, including the interval between zero-point energies (ZPEs) of reagents and product species. Quasi-bound states tend to be more numerous, and eigenlifetimes themselves are seen to increase with J, reaching unusually large values for J = 30. A very dense forest of O3* species is pictured already for J greater than 20, especially at the highest energies considered, leading to a quasi-continuum of metastable states. On the contrary, they appear as rather sparse and isolated at J = 0 and lower energies, including the domain between 18O16O and 16O16O ZPEs, embedded among many overlapping resonances that turn out to be not long-lived enough to be associated with genuine metastable states.
- Published
- 2021
17. Accurate DMBE potential-energy surface for CNO(2A″) and rate coefficients in C(3P)+NO collisions
- Author
-
V. C. Mota, Breno R. L. Galvão, António J. C. Varandas, M. O. Alves, C. E. M. Gonçalves, and João P. Braga
- Subjects
Physics ,Range (particle radiation) ,010304 chemical physics ,Ab initio ,General Physics and Astronomy ,010402 general chemistry ,01 natural sciences ,Molecular physics ,0104 chemical sciences ,0103 physical sciences ,Thermal ,Potential energy surface ,Physical and Theoretical Chemistry ,Dispersion (chemistry) ,Root-mean-square deviation ,Energy (signal processing) - Abstract
A realistic double many-body expansion potential energy surface (PES) is developed for the 2A″ state of the carbon–nitrogen–oxygen (CNO) system based on MRCI-F12/cc-pVQZ-F12 ab initio energies. The new PES reproduces the fitted points with chemical accuracy (root mean square deviation up to 0.043 eV) and explicitly incorporates long range energy terms that can accurately describe the electrostatic and dispersion interactions. Thermal rate coefficients were computed for the C(3P) + NO(2Π) reaction for temperatures ranging from 15 K to 10 000 K, and the values are compared to previously reported results. The differences are rationalized, and the major importance of long range forces in predicting the rate coefficients for barrierless reactions is emphasized.
- Published
- 2021
18. Self-diffusion micromechanism in Nafion studied by 2H NMR relaxation dispersion
- Author
-
Vitaly Sinitsyn, Michael Vogel, Elena A. Galitskaya, I. A. Ryzhkin, and Alexei F. Privalov
- Subjects
Self-diffusion ,Relaxometry ,Range (particle radiation) ,Materials science ,010304 chemical physics ,Proton ,General Physics and Astronomy ,Conductivity ,Atmospheric temperature range ,010402 general chemistry ,01 natural sciences ,0104 chemical sciences ,chemistry.chemical_compound ,chemistry ,Chemical physics ,Nafion ,0103 physical sciences ,Physical and Theoretical Chemistry ,Dispersion (chemistry) - Abstract
Field Cycling (FC) 2H nuclear magnetic resonance (NMR) relaxometry was applied to study dynamics in Nafion NR 212 in the temperature range from 300 K to 190 K and water content of λ = 8.2. The sensitive time window of FC was extended up to eight decades using the temperature–frequency superposition principle and master curve. The rotational correlation times obtained from 2H FC NMR coincide with translational correlation times gained from static field 2H NMR diffusometry in the temperature range applied. This fact means that a long-range mass transport in Nafion is coupled to molecular rotations. It is assumed that confined water in Nafion has more ordered oxygen sublattices as compared with bulk water, on a short range is similar to ice. We discuss the possible role of D and L defects, typical for the ordered ice structure and using this concept to describe the processes of self-diffusion of confined water in Nafion, as well as the similarity of temperature and humidity dependence of self-diffusion and proton conductivity.
- Published
- 2021
19. Polarity Effects of Propylene Carbonate on Breakdown Strength in Microsecond Range
- Author
-
Zhen Wang, Zicheng Zhang, and Jian-de Zhang
- Subjects
chemistry.chemical_compound ,Range (particle radiation) ,Microsecond ,Polarity (physics) ,Chemistry ,Propylene carbonate ,Electrode ,Analytical chemistry ,Breakdown voltage ,Physical and Theoretical Chemistry ,Pulsed power ,Oscilloscope - Abstract
We investigate the polarity effects of the propylene carbonate on the breakdown voltage using the needle-plate electrodes with gaps of 0.5, 1.0, and 2.0 mm. The devices used in this study involve a compact capacitive-energy-storage pulse power source with charging time varying from 5 ms to 20 ms and a test cell with the needle-plate electrodes. The breakdown voltage is recorded by a digital oscilloscope for each gap. The results of these three groups indicate that the positive breakdown voltage is higher than the negative one and the breakdown voltage of the PC increases with the ascending electrode gap. In addition, a simulation is conducted to support this experiment. Some explanations about the polarity effect of the PC are also given.
- Published
- 2015
20. Vibrational predissociation in the bending levels of the à state of C3Ar
- Author
-
Yen-Chu Hsu and Yi Jen Wang
- Subjects
Physics ,Angular momentum ,Range (particle radiation) ,010304 chemical physics ,Binding energy ,Resolution (electron density) ,General Physics and Astronomy ,010402 general chemistry ,01 natural sciences ,Molecular physics ,Fluorescence ,Spectral line ,0104 chemical sciences ,symbols.namesake ,Ab initio quantum chemistry methods ,0103 physical sciences ,symbols ,Physical and Theoretical Chemistry ,van der Waals force - Abstract
Vibrational predissociation (VP) has been observed in 16 bands of the C3Ar van der Waals complex near the 0 v2 0 - 000 (v2 = 2-, 4-, 2+) and 0 2- 2 - 100 bands of the A1Π-X1Σ+g system of C3. New higher resolution wavelength-resolved emission (WRE) spectra covering a wider spectral range have been recorded for many of these C3Ar bands, which show that most of the features observed in fluorescence must be reassigned as emission from the C3 fragment. Two types of VP processes have been recognized. The first type gives rise to vibrationally hot C3 fragments, mostly following |Δv| = 1, |ΔP| = 1 propensity rules, where P is the vibronic angular momentum of C3. The second type gives vibrationally cooled fragments. The VP processes can change abruptly from one type to the other with comparatively small differences in vibrational energy. Although the initial states are associated with both orbital components of the C3, A1Πu state, most of the VP fragments belong to the lower orbital component. A dipole-induced dipole model has been used to interpret the observed ΔP- propensities. Ab initio calculations of the binding energies of the ground and excited electronic states of C3Ar have been carried out; the calculated values are consistent with estimates of ≤144 cm-1 and 164 cm-1, respectively, given by the WRE spectra.
- Published
- 2020
21. Localization model description of the interfacial dynamics of crystalline Cu and Cu64Zr36 metallic glass films
- Author
-
Hao Zhang, Gazi Mahmud, and Jack F. Douglas
- Subjects
Work (thermodynamics) ,Range (particle radiation) ,Materials science ,Amorphous metal ,010304 chemical physics ,Relaxation (NMR) ,General Physics and Astronomy ,010402 general chemistry ,01 natural sciences ,0104 chemical sciences ,Amorphous solid ,Condensed Matter::Soft Condensed Matter ,Mean squared displacement ,Condensed Matter::Materials Science ,Chemical physics ,Picosecond ,0103 physical sciences ,Particle ,Physical and Theoretical Chemistry - Abstract
Recent studies of structural relaxation in Cu-Zr metallic glass materials having a range of compositions and over a wide range of temperatures and in crystalline UO2 under superionic conditions have indicated that the localization model (LM) can predict the structural relaxation time τα of these materials from the intermediate scattering function without any free parameters from the particle mean square displacement ⟨r2⟩ at a caging time on the order of ps, i.e., the "Debye-Waller factor" (DWF). In the present work, we test whether this remarkable relation between the "fast" picosecond dynamics and the rate of structural relaxation τα in these model amorphous and crystalline materials can be extended to the prediction of the local interfacial dynamics of model amorphous and crystalline films. Specifically, we simulate the free-standing amorphous Cu64Zr36 and crystalline Cu films and find that the LM provides an excellent parameter-free prediction for τα of the interfacial region. We also show that the Tammann temperature, defining the initial formation of a mobile interfacial layer, can be estimated precisely for both crystalline and glass-forming solid materials from the condition that the DWFs of the interfacial region and the material interior coincide.
- Published
- 2020
22. Ionizing radiation and natural constituents of living cells: Low-energy electron interaction with coenzyme Q analogs
- Author
-
Nail L. Asfandiarov, Alberto Modelli, Alexey S. Komolov, Stanislav A. Pshenichnyuk, and S.A. Pshenichnyuk, A. Modelli, N.L. Asfandiarov, A.S. Komolov
- Subjects
Ubiquinone ,Cells ,General Physics and Astronomy ,Electrons ,LIFETIME ,Electron ,Radiation ,Photochemistry ,Ionizing radiation ,Ion ,AUTODETACHMENT ,Radiation, Ionizing ,Physical and Theoretical Chemistry ,Spectroscopy ,Density Functional Theory ,AFFINITY ,DAMAGE ,Range (particle radiation) ,Chemistry ,ANION RESONANCES ,Resonance ,TRANSPORT ,ATTACHMENT ,Microsecond ,STATES ,P-BENZOQUINONE ,Thermodynamics ,COENZYME Q10 - Abstract
Resonance electron attachment to short-tail analogs of coenzyme Q10 is investigated in the electron energy range 0 eV-14 eV under gas-phase conditions by means of dissociative electron attachment spectroscopy. Formation of long-lived (milliseconds) molecular negative ions is detected at 1.2 eV, but not at thermal energy. A huge increase in the electron detachment time as compared with the reference para-benzoquinone (40 µs) is ascribed to the presence of the isoprene side chains. Elimination of a neutral CH3 radical is found to be the most intense decay detected on the microsecond time scale. The results give some insight into the timescale of electron-driven processes stimulated in living tissues by high-energy radiation and are of importance in prospective fields of radiobiology and medicine.
- Published
- 2020
23. A stand-alone magnetic guide for producing tuneable radical beams
- Author
-
Brianna R. Heazlewood, Chloé Miossec, M. Hejduk, Lok Yiu Wu, Jutta Toscano, and Paul Bertier
- Subjects
Range (particle radiation) ,Materials science ,010304 chemical physics ,Hydrogen ,Radical ,General Physics and Astronomy ,chemistry.chemical_element ,010402 general chemistry ,Combustion ,01 natural sciences ,0104 chemical sciences ,Magnetic field ,Filter (large eddy simulation) ,chemistry ,Chemical physics ,Impurity ,0103 physical sciences ,Physical and Theoretical Chemistry ,Beam (structure) - Abstract
Radicals are prevalent in gas-phase environments such as the atmosphere, combustion systems, and the interstellar medium. To understand the properties of the processes occurring in these environments, it is helpful to study radical reaction systems in isolation-thereby avoiding competing reactions from impurities. There are very few methods for generating a pure beam of gas-phase radicals, and those that do exist involve complex setups. Here, we provide a straightforward and versatile solution. A magnetic radical filter (MRF), composed of four Halbach arrays and two skimming blades, can generate a beam of velocity-selected low-field-seeking hydrogen atoms. As there is no line-of-sight through the device, all species that are unaffected by the magnetic fields are physically blocked; only the target radicals are successfully guided around the skimming blades. The positions of the arrays and blades can be adjusted, enabling the velocity distribution of the beam (and even the target radical species) to be modified. The MRF is employed as a stand-alone device-filtering radicals directly from the source. Our findings open up the prospect of studying a range of radical reaction systems with a high degree of control over the properties of the radical reactants.
- Published
- 2020
24. Structure and dynamics of the Lennard-Jones fcc-solid focusing on melting precursors
- Author
-
Peter Mausbach, Robin Fingerhut, and Jadran Vrabec
- Subjects
Materials science ,melting precursors ,solid/fluid transition ,General Physics and Astronomy ,Thermodynamics ,Debye-Waller factor ,Cubic crystal system ,numbers of nearest neighbors ,010402 general chemistry ,01 natural sciences ,Displacement (vector) ,Molecular dynamics ,mean-squared displacement ,translational order parameter ,0103 physical sciences ,Physics::Atomic and Molecular Clusters ,541 Physikalische Chemie ,Z method ,Physical and Theoretical Chemistry ,Range (particle radiation) ,010304 chemical physics ,Tammann temperature ,Dynamics (mechanics) ,non-Gaussian parameter ,Pair distribution function ,vibrational density of states ,0104 chemical sciences ,Premelting ,Lennard Jones fcc-solid ,pair distribution function ,Melting point ,ddc:541 - Abstract
This article may be downloaded for personal use only. Any other use requires prior permission of the author and AIP Publishing. This article appeared in J. Chem. Phys. 153, 104506 (2020) and may be found at https://doi.org/10.1063/5.0015371., The Lennard-Jones potential is taken as a basis to study the structure and dynamics of the face centered cubic (fcc) solid along an isochore from low temperatures up to the solid/fluid transition. The Z method is applied to estimate the melting point. Molecular dynamics simulations are used to calculate the pair distribution function, numbers of nearest neighbors, and the translational order parameter, analyzing the weakening of the fcc-symmetry due to emerging premelting effects. A range of dynamic properties, such as the mean-squared displacement, non-Gaussian parameter, Debye–Waller factor, and vibrational density of states, is considered for the analysis of the solid state. All of these parameters clearly show that bulk mobility is activated at about 2/3 of the melting temperature, known as the Tammann temperature. This indicates that vibrational motion of atoms is not maintained exclusively in the entire stable solid state and that collective atomic motion constitutes a precursor of the melting process.
- Published
- 2020
25. Investigation of the low-energy stereodynamics in the Ne(3P2) + N2, CO reactions
- Author
-
Andreas Osterwalder and Junwen Zou
- Subjects
Physics ,Range (particle radiation) ,010304 chemical physics ,General Physics and Astronomy ,010402 general chemistry ,01 natural sciences ,7. Clean energy ,Intermediate product ,0104 chemical sciences ,Ion ,Product (mathematics) ,Ionization ,Excited state ,0103 physical sciences ,Molecule ,Physical and Theoretical Chemistry ,Atomic physics ,Beam (structure) - Abstract
We report on an experimental investigation of the low-energy stereodynamics of the energy transfer reactions Ne(3P2) + X, producing Ne(1S) + X+ and [Ne–X]+ (X = N2 or CO). Collision energies in the range 0.2 K–700 K are obtained by using the merged beam technique. Two kinds of product ions are generated by Penning and associative ionization, respectively. The intermediate product [Ne–X]+ in vibrationally excited states can predissociate into bare ions (X+). The experimental ratio of the NeX+ and X+ product ion yields is similar for both molecules at high collision energies but diverge at collision energies below 100 K. This difference is explained by the first excited electronic state of the product ions, which is accessible in the case of CO but lies too high in energy in the case of N2.
- Published
- 2020
26. Universal reshaping of arrested colloidal gels via active doping
- Author
-
Angelo Cacciuto, M. L. Bowers, and S. A. Mallory
- Subjects
Condensed Matter - Materials Science ,Work (thermodynamics) ,Range (particle radiation) ,Materials science ,Statistical Mechanics (cond-mat.stat-mech) ,010304 chemical physics ,Dispersity ,Doping ,Materials Science (cond-mat.mtrl-sci) ,FOS: Physical sciences ,General Physics and Astronomy ,Condensed Matter - Soft Condensed Matter ,010402 general chemistry ,01 natural sciences ,3. Good health ,0104 chemical sciences ,Suspension (chemistry) ,Colloid ,Chemical physics ,Metastability ,0103 physical sciences ,Active stabilization ,Soft Condensed Matter (cond-mat.soft) ,Physical and Theoretical Chemistry ,Condensed Matter - Statistical Mechanics - Abstract
Colloids that interact via a short-range attraction serve as the primary building blocks for a broad range of self-assembled materials. However, one of the well-known drawbacks to this strategy is that these building blocks rapidly and readily condense into a metastable colloidal gel. Using computer simulations, we illustrate how the addition of a small fraction of purely repulsive self-propelled colloids, a technique referred to as active doping, can prevent the formation of this metastable gel state and drive the system toward its thermodynamically favored crystalline target structure. The simplicity and robust nature of this strategy offers a systematic and generic pathway to improving the self-assembly of a large number of complex colloidal structures. We discuss in detail the process by which this feat is accomplished and provide quantitative metrics for exploiting it to modulate self-assembly. We provide evidence for the generic nature of this approach by demonstrating that it remains robust under a number of different anisotropic short-ranged pair interactions in both two and three dimensions. In addition, we report on a novel microphase in mixtures of passive and active colloids. For a broad range of self-propelling velocities, it is possible to stabilize a suspension of fairly monodisperse finite-size crystallites. Surprisingly, this microphase is also insensitive to the underlying pair interaction between building blocks. The active stabilization of these moderately-sized monodisperse clusters is quite remarkable and should be of great utility in the design of hierarchical self-assembly strategies. This work further bolsters the notion that active forces can play a pivotal role in directing colloidal self-assembly., Comment: Supplemental Material available here: https://aip.scitation.org/doi/suppl/10.1063/5.0016514
- Published
- 2020
27. Energy transfer between vibrationally excited carbon monoxide based on a highly accurate six-dimensional potential energy surface
- Author
-
Joel M. Bowman, Jun Li, Jun Chen, and Hua Guo
- Subjects
Range (particle radiation) ,Materials science ,010304 chemical physics ,Ab initio ,General Physics and Astronomy ,Plasma ,010402 general chemistry ,01 natural sciences ,Molecular physics ,0104 chemical sciences ,Bond length ,Dipole ,Molecular vibration ,Excited state ,0103 physical sciences ,Potential energy surface ,Physical and Theoretical Chemistry - Abstract
Energy transfer between vibrational modes can be quite facile, and it has been proposed as the dominant mechanism for energy pooling in extreme environments such as nonthermal plasmas and laser cavities. To understand such processes, we perform quasi-classical trajectory studies of CO(v) + CO(v) collisions on a new full-dimensional potential energy surface fit to high-level ab initio data using a neural network method and examine the key vibrational energy transfer channels. In addition to the highly efficient CO(v + 1) + CO(v - 1) channel, there exists a significant, sometimes dominant, CO(v + 2) + CO(v - 2) channel for large v states at low collision energies. The latter is shown to stem from the substantially increased interaction between highly vibrationally excited CO, which has a much larger dipole moment than at its equilibrium bond length. Finally, the vibrational state-specific cross sections and their energy dependence on the thermal range are predicted from a limited dataset using Gaussian process regression. The relevance of these results to plasma chemistry and laser engineering and the recently observed flipping of highly vibrationally excited CO adsorbates on a cold NaCl surface is discussed.
- Published
- 2020
28. Impact of particle arrays on phase separation composition patterns
- Author
-
Arnab Mukherjee, Jack F. Douglas, Raymundo Arroyave, and Supriyo Ghosh
- Subjects
Chemical Physics (physics.chem-ph) ,Condensed Matter - Materials Science ,Range (particle radiation) ,Spinodal ,Materials science ,Characteristic length ,Spinodal decomposition ,Materials Science (cond-mat.mtrl-sci) ,FOS: Physical sciences ,General Physics and Astronomy ,Symmetry (physics) ,Wavelength ,Chemical physics ,Physics - Chemical Physics ,Particle ,Lamellar structure ,Physical and Theoretical Chemistry - Abstract
We examine the symmetry-breaking effect of fixed constellations of particles on the surface-directed spinodal decomposition of binary blends in the presence of particles whose surfaces have a preferential affinity for one of the components. Our phase-field simulations indicate that the phase separation morphology in the presence of particle arrays can be tuned to have a continuous, droplet, lamellar, or hybrid morphology depending on the interparticle spacing, blend composition, and time. In particular, when the interparticle spacing is large compared to the spinodal wavelength, a transient target pattern composed of alternate rings of preferred and non-preferred phases emerges at early times, tending to adopt the symmetry of the particle configuration. We reveal that such target patterns stabilize for certain characteristic length, time, and composition scales characteristic of the pure phase-separating mixture. To illustrate the general range of phenomena exhibited by mixture-particle systems, we simulate the effects of single-particle, multi-particle, and cluster-particle systems having multiple geometrical configurations of the particle characteristic of pattern substrates on phase separation. Our simulations show that tailoring the particle configuration, or substrate pattern configuration, a relative fluid-particle composition should allow the desirable control of the phase separation morphology as in block copolymer materials, but where the scales accessible to this approach of organizing phase-separated fluids usually are significantly larger. Limited experiments confirm the trends observed in our simulations, which should provide some guidance in engineering patterned blend and other mixtures of technological interest.
- Published
- 2020
29. The inhibition of concentrated active baths
- Author
-
Hongyuan Jiang and Chen Wang
- Subjects
Range (particle radiation) ,Materials science ,010304 chemical physics ,General Physics and Astronomy ,Péclet number ,010402 general chemistry ,Thermal diffusivity ,01 natural sciences ,0104 chemical sciences ,symbols.namesake ,Volume (thermodynamics) ,Chemical physics ,TRACER ,0103 physical sciences ,Volume fraction ,symbols ,Physical and Theoretical Chemistry ,Diffusion (business) ,Astrophysics::Galaxy Astrophysics ,Brownian motion - Abstract
Passive tracers in the active bath express fascinating behaviors. However, most studies are restricted to dilute active baths. Here, we use 2D simulation of suspensions consisting of active Brownian particles and a passive disk-shaped tracer to investigate tracers' diffusive behaviors in a wide range of volume fractions. Due to the competition between the thermal noise and collisions with active particles, tracers express a first transition from the normal diffusion to the superdiffusion at a short time scale and recur to normal diffusion at a long time scale. At a low volume fraction, infrequent active collisions retard the first transition of smaller tracers. At a high volume fraction, active particles with high activity aggregating around tracers induce a bimodal probability distribution function of tracer displacements during superdiffusion. Considering the enhancement of diffusion, the non-dimensional enhanced diffusivity increases asymptotically with the Peclet number. The asymptotic line gives an upper limit of non-dimensional enhanced diffusivity of tracers. Cases with lower enhanced diffusion have a high volume fraction and a low active velocity that indicates the inhibition of concentrated active baths. With the high negentropic work of these cases, the inhibition is explained as the change of the configuration of active baths for introducing tracers.
- Published
- 2020
30. Erratum: 'Density matrix renormalization group with efficient dynamical electron correlation through range separation' [J. Chem. Phys. 142, 224108 (2015)]
- Author
-
Markus Reiher, H. J. Aa. Jensen, Erik D. Hedegård, Jesper Skau Kielberg, and Stefan Knecht
- Subjects
Physics ,Range (particle radiation) ,010304 chemical physics ,Electronic correlation ,Density matrix renormalization group ,0103 physical sciences ,Separation (statistics) ,General Physics and Astronomy ,Physical and Theoretical Chemistry ,010402 general chemistry ,01 natural sciences ,Molecular physics ,0104 chemical sciences - Published
- 2020
31. Dynamical matrix propagator scheme for large-scale proton dynamics simulations
- Author
-
Christian Dreßler, Martin Brehm, Gabriel Kabbe, and Daniel Sebastiani
- Subjects
Physics ,Range (particle radiation) ,010304 chemical physics ,Basis (linear algebra) ,Markov chain ,Proton ,Stochastic matrix ,General Physics and Astronomy ,Propagator ,010402 general chemistry ,01 natural sciences ,0104 chemical sciences ,Matrix (mathematics) ,0103 physical sciences ,Statistical physics ,Physical and Theoretical Chemistry ,Topology (chemistry) - Abstract
We derive a matrix formalism for the simulation of long range proton dynamics for extended systems and timescales. On the basis of an ab initio molecular dynamics simulation, we construct a Markov chain, which allows us to store the entire proton dynamics in an M × M transition matrix (where M is the number of oxygen atoms). In this article, we start from common topology features of the hydrogen bond network of good proton conductors and utilize them as constituent constraints of our dynamic model. We present a thorough mathematical derivation of our approach and verify its uniqueness and correct asymptotic behavior. We propagate the proton distribution by means of transition matrices, which contain kinetic data from both ultra-short (sub-ps) and intermediate (ps) timescales. This concept allows us to keep the most relevant features from the microscopic level while effectively reaching larger time and length scales. We demonstrate the applicability of the transition matrices for the description of proton conduction trends in proton exchange membrane materials.
- Published
- 2020
32. Activated diffusiophoresis
- Author
-
Mehran Kardar, Matthias Krüger, Christian M. Rohwer, and Massachusetts Institute of Technology. Department of Physics
- Subjects
Physics ,Range (particle radiation) ,Work (thermodynamics) ,Statistical Mechanics (cond-mat.stat-mech) ,Spacetime ,Dynamics (mechanics) ,FOS: Physical sciences ,General Physics and Astronomy ,Motion (geometry) ,02 engineering and technology ,Condensed Matter - Soft Condensed Matter ,021001 nanoscience & nanotechnology ,Electrostatics ,01 natural sciences ,Active matter ,Classical mechanics ,Diffusiophoresis ,0103 physical sciences ,Soft Condensed Matter (cond-mat.soft) ,Physical and Theoretical Chemistry ,010306 general physics ,0210 nano-technology ,Condensed Matter - Statistical Mechanics - Abstract
Perturbations of fluid media can give rise to non-equilibrium dynamics, which may, in turn, cause motion of immersed inclusions or tracer particles. We consider perturbations ("activations") that are local in space and time, of a fluid density which is conserved, and study the resulting diffusiophoretic phenomena that emerge at a large distance. Specifically, we consider cases where the perturbations propagate diffusively, providing examples from passive and active matter for which this is expected to be the case. Activations can, for instance, be realized by sudden and local changes in interaction potentials of the medium or by local changes in its activity. Various analytical results are provided for the case of confinement by two parallel walls. We investigate the possibility of extracting work from inclusions, which are moving through the activated fluid. Furthermore, we show that a time-dependent density profile, created via suitable activation protocols, allows for the conveyance of inclusions along controlled and stable trajectories. In contrast, in states with a steady density, inclusions cannot be held at stable positions, reminiscent of Earnshaw's theorem of electrostatics. We expect these findings to be applicable in a range of experimental systems. The phenomena described here are argued to be distinct from other forms of phoresis such as thermophoresis., NSF (DMR-1708280)
- Published
- 2020
33. Initial steps toward Auad island nucleation on a c(2 × 2)-Cl Au(001) surface investigated by DFT
- Author
-
Alexandra Celinda Dávila López and E. Pehlke
- Subjects
Range (particle radiation) ,Materials science ,010304 chemical physics ,Dimer ,Nucleation ,General Physics and Astronomy ,Trimer ,Electrolyte ,010402 general chemistry ,01 natural sciences ,0104 chemical sciences ,chemistry.chemical_compound ,Crystallography ,Monomer ,chemistry ,Tetramer ,0103 physical sciences ,Density functional theory ,Physical and Theoretical Chemistry - Abstract
Density functional theory calculations are reported that elucidate the initial steps toward Au ad-island nucleation on c(2 × 2)-Cl covered Au(001) surfaces, which is relevant for Au electrodeposition in Cl− containing electrolytes. The atomic geometry of (Auad)n adatom structures for n ≤ 4, as well as their stability as a function of Cl chemical potential, has been determined. The electrolyte, however, has not been accounted for in the computation. We find a weakly bonded (AuadCl2)-chain as the most stable structure in the case of Cl chemical potentials such that Cl vacancies are suppressed. In the range of Cl chemical potential, where Cl vacancies occur in equilibrium and bind to an (modified) Auad induced ad-structure, the formation of a dimer from two monomers is accompanied by an energy gain between 0.06 and 0.23 eV. For Auad trimer and tetramer formation, the calculations suggest a similar tendency. This suggests that on c(2 × 2)-Cl covered Au(001) surfaces, the Au ad-island nucleation is supported by the presence of vacancies in the Cl adlayer.
- Published
- 2020
34. Communication: long range corrections in liquid-vapor interface simulations
- Author
-
Sergey V. Lishchuk and Johann Fischer
- Subjects
Range (particle radiation) ,010304 chemical physics ,Liquid vapor ,Surface integral ,General Physics and Astronomy ,Thermodynamics ,Radius ,010402 general chemistry ,01 natural sciences ,Potential energy ,0104 chemical sciences ,Surface tension ,Leibniz integral rule ,symbols.namesake ,Molecular dynamics ,0103 physical sciences ,symbols ,Physical and Theoretical Chemistry - Abstract
Long range corrections (lrc) for the potential energy and for the force in planar liquid-vapor interface simulations are considered for spherically symmetric interactions. First, it is stated that for the Lennard-Jones (LJ) fluid the lrc for the energy Δu of Janecek [J. Phys. Chem. B 110, 6264 (2006)] is the same as that of Lotfi et al. [Mol. Simul. 5, 233 (1990)]. Second, we present the lrc for the force ΔF for any spherically symmetric interaction as a derivative of Δu plus a surface integral over the cut-off sphere by using the extended Leibniz rule of Flanders [Am. Math. Monthly 80, 615 (1973)]. This ΔF corrects the incomplete lrc Δ1F of Lotfi et al. and agrees with the result of Janecek obtained by direct averaging of the forces. Third, we show that the molecular dynamics (MD) results for the surface tension γ of the LJ fluid with size parameter σ obtained by Werth et al. [Physica A 392, 2359 (2013)] with the lrc ΔF of Janecek and a cut-off radius rc = 3σ agree with the results of Mecke et al. [J. Chem. Phys. 107, 9264 (1997)] obtained with the lrc Δ1F of Lotfi et al. and rc = 6.5σ within −0.4% to +1.6%. Moreover, using only the MD results for γ of Werth et al., we obtain for the LJ fluid a new surface tension correlation which also represents the γ-values of Mecke et al. within ±0.7%. The critical temperature resulting from the correlation is Tc = 1.317 66 and is in very good agreement with Tc,ref = 1.32 of the reference equation of state for the LJ fluid given by Thol et al. [J. Phys. Chem. Ref. Data 45, 023101 (2016)].
- Published
- 2018
35. The complex behavior of the 'simplest' liquid: Breakdown of density scaling in tetramethyl tetraphenyl trisiloxane
- Author
-
T. C. Ransom, Daniel Fragiadakis, Riccardo Casalini, and C. M. Roland
- Subjects
Range (particle radiation) ,Materials science ,010304 chemical physics ,General Physics and Astronomy ,Thermodynamics ,Dielectric ,010402 general chemistry ,01 natural sciences ,Density scaling ,0104 chemical sciences ,0103 physical sciences ,Exponent ,Relaxation (physics) ,Physical and Theoretical Chemistry ,Dispersion (chemistry) ,Constant (mathematics) ,Scaling - Abstract
Dielectric relaxation measurements, in combination with density determinations, on tetramethyl tetraphenyl trisiloxane (DC704) over an unusually broad range of temperatures and pressures revealed a state-point dependency in its density scaling exponent. This is the first unambiguous experimental demonstration of a breakdown of density scaling in a nonassociated glass-forming material, and unanticipated for DC704, among the "simplest" of liquids, having a constant breadth of the relaxation dispersion and a Prigogine-Defay ratio near unity characteristic of approximate single-parameter systems. We speculate that the anomalous behavior has origins in the large value of its scaling exponent and relative flexibility of the chemical structure.
- Published
- 2019
36. Asymmetric and long range interactions in shaken granular media
- Author
-
Ignacio Pagonabarraga, Joan Codina, and Universitat de Barcelona
- Subjects
FOS: Physical sciences ,General Physics and Astronomy ,Granular media ,Condensed Matter - Soft Condensed Matter ,010402 general chemistry ,Kinetic energy ,01 natural sciences ,Stochastic processes ,0103 physical sciences ,Torque ,Physical and Theoretical Chemistry ,Physics ,Granular materials ,Range (particle radiation) ,010304 chemical physics ,Nonequilibrium statistical mechanics ,Time evolution ,Processos estocàstics ,Mechanics ,Function (mathematics) ,Materials granulars ,0104 chemical sciences ,Sphere packing ,Amplitude ,Soft Condensed Matter (cond-mat.soft) ,Mecànica estadística del no equilibri - Abstract
We use a computational model to investigate the emergence of interaction forces between pairs of intruders in a horizontally vibrated granular fluid. The time evolution of a pair of particles shows a maximum of the likelihood to find the pair at contact in the direction of shaking. This relative interaction is further studied by fixing the intruders in the simulation box where we identify effective mechanical forces and torques between particles and quantify an emergent long range attractive force as a function of the shaking relative angle, the amplitude, and the packing density of grains. We determine the local density and kinetic energy profiles of granular particles along the axis of the dimer to find no gradients in the density fields and additive gradients in the kinetic energies.
- Published
- 2019
37. Accurate Measurement of Raman Depolarization Ratio in Gaseous CO2
- Author
-
Yuxi Wang, Yu-juan Jin, Shilin Liu, Xiaoguo Zhou, Ke Lin, and Yuanqin Yu
- Subjects
inorganic chemicals ,Range (particle radiation) ,business.industry ,Chemistry ,Photoacoustic imaging in biomedicine ,Depolarization ,symbols.namesake ,Optics ,symbols ,Depolarization ratio ,Coherent anti-Stokes Raman spectroscopy ,Physical and Theoretical Chemistry ,Signal intensity ,Raman spectroscopy ,business ,Laser beams - Abstract
The Raman depolarization ratios of gaseous CO2 in the spectral range of 1240–1430 cm−1 are determined with a sensitive photoacoustic Raman spectroscopy, and more accurate data compared to the literature results are presented. The precision of the obtained depolarization ratio is achieved by measuring and fitting the dependence of the PARS signal intensity on the cross angle between the polarizations of two incident laser beams.
- Published
- 2015
38. Synthesis of Silica Particles with Precisely Tailored Diameter
- Author
-
Lei Pan, Yi Wang, Jiupeng Zhao, Hongbo Xu, Yao Li, and Yan-bo Ding
- Subjects
chemistry.chemical_compound ,Range (particle radiation) ,Materials science ,Chemical engineering ,Dynamic light scattering ,chemistry ,Band gap ,Silica particle ,Nanotechnology ,Physical and Theoretical Chemistry ,Photonic crystal ,Tetraethyl orthosilicate - Abstract
A modified seeded growth process of silica particles with a continuous addition of tetraethyl orthosilicate (TEOS) was presented to control the diameter of silica particles. The diameter of particles was monitored by dynamic light scattering to control the addition of TEOS. The increase in the diameter of the silica particles with time and the addition of TEOS was investigated. The diameter of silica seeds increased from 193 nm to 446 nm in 4 h. The final diameter of silica particles was tailored within the range of ±5 nm to the target diameter. Silica particles with diameter of 446 nm were synthesized and assembled into photonic crystals with a pseudo band gap centered at just 1000 nm. The feasibility and practicability of this modified seeded growth process was verified.
- Published
- 2014
39. Ultraslow radiative cooling of Cn− (n = 3–5)
- Author
-
Najeeb Punnakayathil, Gustav Eklund, M. K. Kristiansson, Henrik Cederquist, Eduardo Carrascosa, Michael S. Scholz, Mark H. Stockett, Henning T. Schmidt, Henning Zettergren, James N. Bull, and Nathalie de Ruette
- Subjects
spectroscopy ,Radiative cooling ,Infrared ,FOS: Physical sciences ,General Physics and Astronomy ,c6h ,010402 general chemistry ,01 natural sciences ,Spectral line ,Ion ,Physics - Chemical Physics ,0103 physical sciences ,Radiative transfer ,molecules ,c-4(-) ,Physics - Atomic and Molecular Clusters ,Physics::Atomic Physics ,Physics::Chemical Physics ,Physical and Theoretical Chemistry ,Adiabatic process ,Chemical Physics (physics.chem-ph) ,Physics ,negative-ions ,Range (particle radiation) ,010304 chemical physics ,circumstellar shell ,Astrophysics - Astrophysics of Galaxies ,0104 chemical sciences ,internal-conversion ,Wavelength ,Astrophysics of Galaxies (astro-ph.GA) ,range ,astronomical detection ,Atomic physics ,Atomic and Molecular Clusters (physics.atm-clus) - Abstract
Ultraslow radiative cooling lifetimes and adiabatic detachment energies for three astrochemically relevant anions, Cn- (n = 3-5), are measured using the Double ElectroStatic Ion Ring ExpEriment (DESIREE) infrastructure at Stockholm University. DESIREE maintains a background pressure of approximate to 10(-14) mbar and temperature of approximate to 13 K, allowing storage of mass-selected ions for hours and providing conditions coined a "molecular cloud in a box." Here, we construct two-dimensional (2D) photodetachment spectra for the target anions by recording photodetachment signal as a function of irradiation wavelength and ion storage time (seconds to minute time scale). Ion cooling lifetimes, which are associated with infrared radiative emission, are extracted from the 2D photodetachment spectrum for each ion by tracking the disappearance of vibrational hot-band signal with ion storage time, giving 1e cooling lifetimes of 3.1 +/- 0.1 s (C3-), 6.8 +/- 0.5 s (C4-), and 24 +/- 5 s (C5-). Fits of the photodetachment spectra for cold ions, i.e., those stored for at least 30 s, provide adiabatic detachment energies in good agreement with values from laser photoelectron spectroscopy on jet-cooled anions, confirming that radiative cooling has occurred in DESIREE. Ion cooling lifetimes are simulated using a simple harmonic cascade model, finding good agreement with experiment and providing a mode-by-mode understanding of the radiative cooling properties. The 2D photodetachment strategy and radiative cooling modeling developed in this study could be applied to investigate the ultraslow cooling dynamics of a wide range of molecular anions.
- Published
- 2019
40. Experimental validation of interpolation method for pair correlations in model crystals
- Author
-
Egor V. Yakovlev, Stanislav O. Yurchenko, Andrei V. Sapelkin, Manis Chaudhuri, Pavel V. Ovcharov, and Nikita P. Kryuchkov
- Subjects
Physics ,Range (particle radiation) ,010304 chemical physics ,General Physics and Astronomy ,Plasma ,Colloidal crystal ,010402 general chemistry ,01 natural sciences ,Measure (mathematics) ,0104 chemical sciences ,Molecular dynamics ,0103 physical sciences ,Monolayer ,Soft matter ,Statistical physics ,Physical and Theoretical Chemistry ,Interpolation - Abstract
Accurate analysis of pair correlations in condensed matter allows us to establish relations between structures and thermodynamic properties and, thus, is of high importance for a wide range of systems, from solids to colloidal suspensions. Recently, the interpolation method (IM) that describes satisfactorily the shape of pair correlation peaks at short and at long distances has been elaborated theoretically and using molecular dynamics simulations, but it has not been verified experimentally as yet. Here, we test the IM by particle-resolved studies with colloidal suspensions and with complex (dusty) plasmas and demonstrate that, owing to its high accuracy, the IM can be used to experimentally measure parameters that describe interaction between particles in these systems. We used three- and two-dimensional colloidal crystals and monolayer complex (dusty) plasma crystals to explore suitability of the IM in systems with soft to hard-sphere-like repulsion between particles. In addition to the systems with pairwise interactions, if many-body interactions can be mapped to the pairwise ones with some effective (e.g., density-dependent) parameters, the IM could be used to obtain these parameters. The results reliably show that the IM can be effectively used for analysis of pair correlations and interactions in a wide variety of systems and therefore is of broad interest in condensed matter, complex plasma, chemical physics, physical chemistry, materials science, and soft matter.
- Published
- 2019
41. Diffusion of interacting particles in a channel with reflection boundary conditions
- Author
-
Narender Khatri and P. S. Burada
- Subjects
Range (particle radiation) ,Materials science ,010304 chemical physics ,business.industry ,FOS: Physical sciences ,General Physics and Astronomy ,Condensed Matter - Soft Condensed Matter ,010402 general chemistry ,01 natural sciences ,0104 chemical sciences ,Nonlinear system ,Reflection (mathematics) ,Chemical physics ,0103 physical sciences ,Soft Condensed Matter (cond-mat.soft) ,Boundary value problem ,Physical and Theoretical Chemistry ,Diffusion (business) ,business ,Scaling ,Brownian motion ,Thermal energy - Abstract
The diffusive transport of biased Brownian particles in a two-dimensional symmetric channel is investigated numerically considering both the no-flow and the reflection boundary conditions at the channel boundaries. Here, the geometrical confinement leads to entropic barriers which effectively control the transport properties of the particles. We show that compared to no-flow boundary conditions, the transport properties exhibit distinct features in a channel with reflection boundary conditions. For example, the nonlinear mobility exhibits a nonmonotonic behavior as a function of the scaling parameter $f$, which is a ratio of the work done to the particles to available thermal energy. Also, the effective diffusion exhibits a rapidly increasing behavior at higher $f$. The nature of reflection, i.e., elastic or inelastic, also influences the transport properties firmly. We find that inelastic reflections increase both the mobility and the effective diffusion for smaller $f$. In addition, by including the short range interaction force between the Brownian particles, the mobility decreases and the effective diffusion increases for various values of $f$. These findings, which are a signature of the entropic nature of the system, can be useful to understand the transport of small particles or molecules in systems such as microfluidic channels, membrane pores, and molecular sieves., Comment: 17 Pages, 7 Figures, Manuscript Accepted in 2019
- Published
- 2019
42. Localization model description of diffusion and structural relaxation in superionic crystalline UO2
- Author
-
Xinyi Wang, Jack F. Douglas, and Hao Zhang
- Subjects
Range (particle radiation) ,Amorphous metal ,Materials science ,010304 chemical physics ,Relaxation (NMR) ,Anharmonicity ,General Physics and Astronomy ,010402 general chemistry ,01 natural sciences ,0104 chemical sciences ,Ion ,Chemical physics ,Picosecond ,0103 physical sciences ,Physical and Theoretical Chemistry ,Diffusion (business) ,Free parameter - Abstract
We test the Localization Model (LM) prediction of a parameter-free relationship between the α-structural relaxation time τα and the oxygen ion diffusion coefficient DO with the Debye-Waller factor ⟨u2⟩ for crystalline UO2 under superionic conditions where large anharmonic interactions lead to non-Arrhenius relaxation and high ion mobility. As in a previous study of structural relaxation in Cu–Zr metallic glass materials having a range of compositions, we find that the LM relationship between the picosecond atomic dynamics (“fast” beta relaxation) and the long-time structural relaxation time and oxygen ion diffusion coefficient holds to an excellent approximation without any free parameters over the full range of temperatures and pressures investigated in our simulations.
- Published
- 2019
43. Effects of interionic non-hard sphere neutral interaction and solvent crowding on differential capacitance curve of electrical double layer
- Author
-
S. Zhou
- Subjects
chemistry.chemical_classification ,Range (particle radiation) ,Materials science ,010304 chemical physics ,Differential capacitance ,General Physics and Astronomy ,Thermodynamics ,Electrolyte ,010402 general chemistry ,01 natural sciences ,0104 chemical sciences ,Ion ,Adsorption ,chemistry ,0103 physical sciences ,Density functional theory ,Surface charge ,Physical and Theoretical Chemistry ,Counterion - Abstract
By using classical density functional theory, we study the effects of interionic nonhard sphere neutral interaction (NHSNI) and solvent crowding on curve of differential electrical capacitance (Cd) vs surface charge strength |σ| of an electrical double layer (EDL) formed inside a cylindrical pore electrode. Main new findings are summarized as follows. (i) Increasing the intercounterion neutral attractive interaction helps in raising the Cd − |σ| curve and vice versa; the lowering or enhancing effect continues until rather high |σ|, such as |σ| = 1 C m−2. (ii) Attractive NHSNI between coion and counterion lowers the Cd − |σ| curve and vice versa; the lowering or enhancing effect quickly becomes very weak with |σ|. (iii) The lowering or enhancing effect strength of the intercounterion NHSNI potential range is negatively correlated with the bulk electrolyte concentration, whereas the correlation becomes positive for the potential range of the NHSNI between coion and counterion. (iv) Whether the bulk concentration is high or low, one stronger intercounterion attractive NHSNI tends to induce one more obvious peak of the Cd − |σ| curve at higher |σ|; only after this peak, the intercounterion NHSNI does not influence the Cd − |σ| curve obviously. However, the peak does not come with one intercounterion repulsive NHSNI and any kind of NHSNI between coion and counterion. (v) The solvent crowding induced by its granularity generally raises the Cd curve when |σ| is low and moderate, but the enhancing effect tends to become unobservable with further rising of |σ|. The above findings are explained reasonably by analyzing the ions local distributions in the EDL, their adsorption capacities, and the peak of change rate of the total ion adsorption capacity with |σ|.
- Published
- 2019
44. From the molecular quadrupole moment of oxygen to the macroscopic quadrupolarizability of its liquid phase
- Author
-
Angiras Menon, Iglika M. Dimitrova, and Radomir I. Slavchov
- Subjects
Work (thermodynamics) ,Range (particle radiation) ,Materials science ,010304 chemical physics ,Condensed matter physics ,Computation ,Physics::Optics ,General Physics and Astronomy ,Dielectric ,010402 general chemistry ,01 natural sciences ,0104 chemical sciences ,Condensed Matter::Soft Condensed Matter ,0103 physical sciences ,Moment (physics) ,Quadrupole ,Molecule ,Physics::Chemical Physics ,Physical and Theoretical Chemistry ,Liquid oxygen - Abstract
Liquid oxygen is an example for a quadrupolar medium—a dense fluid made of nonpolar molecules carrying a significant quadrupolar moment. In this work, we present a method for the computation of the macroscopic quadrupolarizability of such a quadrupolar liquid. As a first step, the quadrupole moment and the molecular quadrupolarizability of O2 are calculated from first principles. Next, we apply a model generalizing Onsager’s dielectric cavity theory to compute the macroscopic quadrupolarizability of liquid oxygen under a wide range of conditions. Literature data for the density and dielectric permittivity of oxygen are used to determine the cavity size independently.Liquid oxygen is an example for a quadrupolar medium—a dense fluid made of nonpolar molecules carrying a significant quadrupolar moment. In this work, we present a method for the computation of the macroscopic quadrupolarizability of such a quadrupolar liquid. As a first step, the quadrupole moment and the molecular quadrupolarizability of O2 are calculated from first principles. Next, we apply a model generalizing Onsager’s dielectric cavity theory to compute the macroscopic quadrupolarizability of liquid oxygen under a wide range of conditions. Literature data for the density and dielectric permittivity of oxygen are used to determine the cavity size independently.
- Published
- 2019
45. Entrance effects in concentration-gradient-driven flow through an ultrathin porous membrane
- Author
-
Daniel J. Rankin, David M. Huang, Lydéric Bocquet, University of Adelaide, Laboratoire de Physique Statistique de l'ENS (LPS), Université Paris Diderot - Paris 7 (UPD7)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Centre National de la Recherche Scientifique (CNRS)-Fédération de recherche du Département de physique de l'Ecole Normale Supérieure - ENS Paris (FRDPENS), École normale supérieure - Paris (ENS Paris), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS)-École normale supérieure - Paris (ENS Paris), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS), Micromegas : Nano-Fluidique, Laboratoire de physique de l'ENS - ENS Paris (LPENS (UMR_8023)), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS)-Sorbonne Université (SU)-Université Paris Diderot - Paris 7 (UPD7)-École normale supérieure - Paris (ENS Paris), and Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS)-Sorbonne Université (SU)-Université Paris Diderot - Paris 7 (UPD7)
- Subjects
Materials science ,Flow (psychology) ,FOS: Physical sciences ,General Physics and Astronomy ,Condensed Matter - Soft Condensed Matter ,010402 general chemistry ,7. Clean energy ,01 natural sciences ,Desalination ,Nanomaterials ,Quantitative Biology::Subcellular Processes ,Physics - Chemical Physics ,Electric field ,Mesoscale and Nanoscale Physics (cond-mat.mes-hall) ,0103 physical sciences ,[PHYS.COND]Physics [physics]/Condensed Matter [cond-mat] ,[PHYS.COND.CM-SM]Physics [physics]/Condensed Matter [cond-mat]/Statistical Mechanics [cond-mat.stat-mech] ,Physical and Theoretical Chemistry ,Scaling ,ComputingMilieux_MISCELLANEOUS ,Pressure gradient ,[PHYS]Physics [physics] ,Chemical Physics (physics.chem-ph) ,Condensed Matter - Materials Science ,Physics::Biological Physics ,Range (particle radiation) ,Condensed Matter - Mesoscale and Nanoscale Physics ,010304 chemical physics ,Fluid Dynamics (physics.flu-dyn) ,Materials Science (cond-mat.mtrl-sci) ,Physics - Fluid Dynamics ,6. Clean water ,0104 chemical sciences ,Membrane ,Chemical physics ,Soft Condensed Matter (cond-mat.soft) ,[PHYS.COND.CM-SCM]Physics [physics]/Condensed Matter [cond-mat]/Soft Condensed Matter [cond-mat.soft] - Abstract
Transport of liquid mixtures through porous membranes is central to processes such as desalination, chemical separations, and energy harvesting, with ultrathin membranes made from novel 2D nanomaterials showing exceptional promise. Here, we derive, for the first time, general equations for the solution and solute fluxes through a circular pore in an ultrathin planar membrane induced by a solute concentration gradient. We show that the equations accurately capture the fluid fluxes measured in finite-element numerical simulations for weak solute–membrane interactions. We also derive scaling laws for these fluxes as a function of the pore size and the strength and range of solute–membrane interactions. These scaling relationships differ markedly from those for concentration-gradient-driven flow through a long cylindrical pore or for flow induced by a pressure gradient or an electric field through a pore in an ultrathin membrane. These results have broad implications for transport of liquid mixtures through membranes with thickness on the order of the characteristic pore size.Transport of liquid mixtures through porous membranes is central to processes such as desalination, chemical separations, and energy harvesting, with ultrathin membranes made from novel 2D nanomaterials showing exceptional promise. Here, we derive, for the first time, general equations for the solution and solute fluxes through a circular pore in an ultrathin planar membrane induced by a solute concentration gradient. We show that the equations accurately capture the fluid fluxes measured in finite-element numerical simulations for weak solute–membrane interactions. We also derive scaling laws for these fluxes as a function of the pore size and the strength and range of solute–membrane interactions. These scaling relationships differ markedly from those for concentration-gradient-driven flow through a long cylindrical pore or for flow induced by a pressure gradient or an electric field through a pore in an ultrathin membrane. These results have broad implications for transport of liquid mixtures through m...
- Published
- 2019
46. Transitions in pressure-amorphized clathrate hydrates akin to those of amorphous ices
- Author
-
Ying-Jui Hsu, Ulrich Häussermann, Paulo H. B. Brant Carvalho, and Ove Andersson
- Subjects
Range (particle radiation) ,Materials science ,010304 chemical physics ,Clathrate hydrate ,Nucleation ,General Physics and Astronomy ,Thermodynamics ,Activation energy ,Dielectric ,010402 general chemistry ,01 natural sciences ,Heat capacity ,0104 chemical sciences ,Amorphous solid ,0103 physical sciences ,Amorphous ice ,Physical and Theoretical Chemistry - Abstract
Type II clathrate hydrates (CHs) were studied by thermal and dielectric measurements. All CHs amorphize, or collapse, on pressurization to 1.3 GPa below 135 K. After heating to 160 K at 1 GPa, the stability of the amorphous states increases in a process similar to the gradual high density to very high density amorphous ice (HDA to VHDA) transition. On a subsequent pressure decrease, the amorphized CHs expand partly irreversibly similar to the gradual VHDA to expanded HDA ice transformation. After further heating at 1 GPa, weak transition features appear near the HDA to low density amorphous ice transition. The results suggest that CH nucleation sites vanish on heating to 160 K at 1 GPa and that a sluggish partial phase-separation process commences on further heating. The collapsed CHs show two glass transitions (GTs), GT1 and GT2. GT1 is weakly pressure-dependent, 12 K GPa-1, with a relaxation time of 0.3 s at 140 K and 1 GPa; it is associated with a weak heat capacity increase of 3.7 J H2O-mol-1 K-1 in a 18 K range and an activation energy of only 38 kJ mol-1 at 1 GPa. The corresponding temperature of GT2 is 159 K at 0.4 GPa with a pressure dependence of 36 K GPa-1; it shows 5.5 times larger heat capacity increase and 4 times higher activation energy than GT1. GT1 is observed also in HDA and VHDA, whereas GT2 occurs just above the crystallization temperature of expanded HDA and only within its ∼0.2-0.7 GPa stable pressure range.
- Published
- 2019
47. Phase separation in binary fluid mixtures with symmetric and asymmetric Schmidt numbers: A DPD study
- Author
-
Mahesh V. Panchagnula, Srikanth Vedantam, Harinadha Gidituri, and V. S. Akella
- Subjects
Physics ,Range (particle radiation) ,Binary fluid ,010304 chemical physics ,Dynamics (mechanics) ,Dissipative particle dynamics ,Schmidt number ,General Physics and Astronomy ,Thermodynamics ,010402 general chemistry ,01 natural sciences ,Power law ,0104 chemical sciences ,0103 physical sciences ,Exponent ,Physical and Theoretical Chemistry ,Characteristic exponent - Abstract
We investigate the effect of the Schmidt number (Sc) on phase separation dynamics of two immiscible fluids in a two-dimensional periodic box using dissipative particle dynamics. The range of Sc investigated spans liquid-liquid separation processes. Phase separation is characterized by a domain size r(t), which typically follows a power law tβ in time t, where β is a characteristic exponent corresponding to the coarsening mechanism at play. The phase separation dynamics is studied for strongly (deep quench) separating mixtures. We consider cases of critical (ϕ ∼ 0.5) and off-critical (ϕ < 0.5) mixtures of fluids A and B for both ScA = ScB and ScA ≠ ScB. In all cases, the growth dynamics slow down with the increasing Schmidt number of either fluid. We observe the power law exponent β = 0.5 for symmetric (ScA = ScB) critical mixtures and β = 0.33 for all other cases. However, for off-critical mixtures, the exponent is 0.33 irrespective of the Schmidt number ratio of the two fluids. We explain these results from an analysis of the competition between diffusive effects vis-a-vis dynamical forces.
- Published
- 2019
48. Investigation of structural ordering in network forming ionic liquids: A molecular dynamics study
- Author
-
Alejandro Strachan and Karthik Guda Vishnu
- Subjects
Range (particle radiation) ,Materials science ,010304 chemical physics ,General Physics and Astronomy ,Trapping ,010402 general chemistry ,01 natural sciences ,Gyration ,0104 chemical sciences ,Molecular dynamics ,chemistry.chemical_compound ,Molecular geometry ,chemistry ,Chemical physics ,0103 physical sciences ,Ionic liquid ,Side chain ,Molecule ,Physical and Theoretical Chemistry - Abstract
Molecular dynamics simulations reveal anomalous short- and medium-range ordering with increasing temperature in network-forming ionic liquids (NIL) consisting of alkyl-diammonium cations with long side chains of 6 carbon atoms and citrate anions (NIL 5-6). This effect is weaker, and only a short-range order is observed in equivalent systems with side chains shortened to 3 C atoms (NIL 5-3). The short-range ordering can be attributed to volume expansion during heating, but the intermediate range order requires volume expansion as well as an increase in temperature. We find that the cross (cation-anion) interactions are the major contributors to the observed trend and the development of complex 3D correlations in the two-particle correlation functions. The simulations suggest that the above phenomenon can be correlated to local trapping of cation molecules in a variety of configurations at lower temperatures where molecular shape distributions show great variability; as temperature increases, the distribution of molecular radii of gyration becomes narrower, enabling the increased ordering.
- Published
- 2019
49. A new equation of state for homo-polymers in dissipative particle dynamics
- Author
-
Sumanth N. Jamadagni, David M. Eike, Robert H. Hembree, Ahmad F. Ghobadi, J. Ilja Siepmann, and Mona S. Minkara
- Subjects
Equation of state ,Range (particle radiation) ,Number density ,Materials science ,010304 chemical physics ,Dissipative particle dynamics ,General Physics and Astronomy ,Thermodynamics ,010402 general chemistry ,01 natural sciences ,0104 chemical sciences ,Bond length ,Virial coefficient ,0103 physical sciences ,Physical and Theoretical Chemistry ,Perturbation theory ,Constant (mathematics) - Abstract
A chain-revised Groot-Warren equation of state (crGW-EOS) was developed and tested to describe systems of homo-oligomeric chains in the framework of dissipative particle dynamics (DPD). First, thermodynamic perturbation theory is applied to introduce correction terms that account for the reduction in pressure with an increasing number of bonds at constant bead number density. Then, this EOS is modified by introducing a set of switching functions that yields an accurate second virial coefficient in the low-density limit. The crGW-EOS offers several improvements over the revised Groot-Warren equation of state and Groot-Warren equation of state for chain molecules. We tested the crGW-EOS by using it to predict the pressure of oligomeric systems and the B2 virial coefficient of chain DPD particles for a range of bond lengths. Additionally, a method is developed for determining the strength of cross-interaction parameters between chains of different compositions and sizes and for thermal and athermal mixtures. We explored how different levels of coarse-graining affect the upper-critical solution temperature.
- Published
- 2019
50. Range-separated multideterminant density-functional theory with a short-range correlation functional of the on-top pair density
- Author
-
Emmanuel Giner, Anthony Ferté, Julien Toulouse, Laboratoire de chimie théorique (LCT), and Institut de Chimie du CNRS (INC)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)
- Subjects
Chemical Physics (physics.chem-ph) ,Physics ,Range (particle radiation) ,010304 chemical physics ,Density gradient ,FOS: Physical sciences ,General Physics and Astronomy ,Computational Physics (physics.comp-ph) ,010402 general chemistry ,01 natural sciences ,Molecular physics ,Bond-dissociation energy ,0104 chemical sciences ,[PHYS.PHYS.PHYS-COMP-PH]Physics [physics]/Physics [physics]/Computational Physics [physics.comp-ph] ,Physics - Chemical Physics ,0103 physical sciences ,Molecule ,Density functional theory ,[PHYS.PHYS.PHYS-CHEM-PH]Physics [physics]/Physics [physics]/Chemical Physics [physics.chem-ph] ,Physical and Theoretical Chemistry ,Asymptotic expansion ,Wave function ,Physics - Computational Physics ,Energy functional - Abstract
We introduce an approximation to the short-range correlation energy functional with multide-terminantal reference involved in a variant of range-separated density-functional theory. This approximation is a local functional of the density, the density gradient, and the on-top pair density, which locally interpolates between the standard Perdew-Burke-Ernzerhof correlation functional at vanishing range-separation parameter and the known exact asymptotic expansion at large range-separation parameter. When combined with (selected) configuration-interaction calculations for the long-range wave function, this approximation gives accurate dissociation energy curves of the H2, Li2, and Be2 molecules, and thus appears as a promising way to accurately account for static correlation in range-separated density-functional theory., The Journal of Chemical Physics, In press
- Published
- 2019
Catalog
Discovery Service for Jio Institute Digital Library
For full access to our library's resources, please sign in.