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In this work, the effect of two organic polyamines (spermine and spermidine) on the fluorescence intensity and activity of bovine intestinal alkaline phosphatase (BIALP) are investigated. The interaction of BIALP with spermine and spermidine was studied in a diethanolamine buffer with 0.5 mM magnesium chloride (pH 9.8) and at two temperatures by using the fluorescence quenching method. Furthermore, the activity of enzyme was studied using UV–Vis spectrophotometry in a diethanolamine buffer with 0.5 mM magnesium chloride, at 37 °C, in the absence and presence of different concentrations of each polyamine (0–5 mM). It was demonstrated that both polyamines quenched the intrinsic fluorescence of BIALP by the static quenching process. Based on these results, the values of the binding site for both polyamines were close to each other and decreased by increasing the temperature. The calculated thermodynamic parameters (ΔH°

The extreme resolution of CO 2 gas molecules sensing, i.e., detection of single molecule, is reported. The suspended bilayer graphene beam is exploited in order to isolate the sensing part of the device from the substrate noise. Using the electrostatic force, the central part of the suspended beam is pulled-down to bottom metal electrode, which leads to two slanted graphene beams in suspension with built-in tensile strain. This novel design of suspended graphene beam architecture avoids any further mechanical deflection of pulled-down beams on to the substrate when the electric field is applied from the substrate. The step-like changes in the graphene beam resistance with a quantized value of ∼62 Ω are measured when exposed to low concentration CO 2 molecules. These discrete responses are clear evidence to individual CO 2 molecule adsorption onto the slanted graphene beam. In order to enhance the molecular adsorption rate, the electrical field is introduced around the suspended graphene region by applying the back-gate voltage. The first-principles calculations and molecular dynamics simulations elucidate the role of van der Waals interaction between molecules and graphene during detection and the back gate effects on accelerating the molecules adsorption.

The BOUND program calculates the bound states of a complex formed from two interacting particles using coupled-channel methods. It is particularly suitable for the bound states of atom-molecule and molecule-molecule Van der Waals complexes and for the near-threshold bound states that are important in ultracold physics. It uses a basis set for all degrees of freedom except $R$, the separation of the centres of mass of the two particles. The Schr\"odinger equation is expressed as a set of coupled equations in $R$. Solutions of the coupled equations are propagated outwards from the classically forbidden region at short range and inwards from the classically forbidden region at long range, and matched at a point in the central region. Built-in coupling cases include atom + rigid linear molecule, atom + vibrating diatom, atom + rigid symmetric top, atom + asymmetric or spherical top, rigid diatom + rigid diatom, and rigid diatom + asymmetric top. Both programs provide an interface for plug-in routines to specify coupling cases (Hamiltonians and basis sets) that are not built in. With appropriate plug-in routines, BOUND can take account of the effects of external electric, magnetic and electromagnetic fields, locating bound-state energies at fixed values of the fields. The related program FIELD uses the same plug-in routines and locates values of the fields where bound states exist at a specified energy. As a special case, it can locate values of the external field where bound states cross scattering thresholds and produce zero-energy Feshbach resonances. Plug-in routines are supplied to handle the bound states of a pair of alkali-metal atoms with hyperfine structure in an applied magnetic field., Comment: One of two parallel papers that document the MOLSCAT, BOUND and FIELD programs, which use closely related theoretical methods but serve different purposes. This paper and arXiv:1811.09584 therefore have substantial text overlap

In this paper, we have presented generalized closed form solutions to estimate the permissible dimensional limits for the basic design parameters as well as the accurate pull-in characteristics of electrostatically actuated fixed-fixed nano beam. The coupled electromechanical problem for the nano beam is formulated using Galerkin's approximation while considering the effects of fringe field, mid-plane stretching and intermolecular forces like van der Waals and Casimir. The resulting integrals and higher order polynomials are solved numerically to determine the closed form expressions for allowable detachment length, minimum feasible gap, and critical pull-in parameters. The derived expressions are compared quantitatively with other reported results which show reasonable agreement. The advantage here is that the derived expressions do not involve any complex mathematical operation unlike in existing literature, and thus the expressions can be readily used for quick and accurate estimation of the design parameters. As the applied voltage exceeds beyond pull-in limit, it can lead to severe structural failure during operation; hence the designers must be aware of the accurate pull-in expressions as derived in this paper. It has been observed that the incorporation of the intermolecular forces together with the fringe effect leads to significant reduction in pull-in voltage whereas the mid-plane stretching parameter shows the opposite effect. It is further envisaged that, the proposed generalized closed form expressions will serve as quick guidelines for reliable and safe design and fabrication of various similar electrostatically actuated nanosystems.

Stacks of 2-D materials, known as van der Waals (vdW) heterostructures, have gained vast attention due to their interesting electrical and optoelectronic properties. This paper presents an intuitive circuit model for the out-of-plane electrostatics of a vdW heterostructure composed of an arbitrary number of layers of 2-D semiconductors, graphene, or metal. We explain the mapping between the out-of-plane energy band diagram and the elements of the equivalent circuit. Although the direct solution of the circuit model for an n-layer structure is not possible due to the variable, nonlinear quantum capacitance of each layer, this paper uses the intuition gained from the energy band picture to provide an efficient solution in terms of a single variable. Our method employs Fermi–Dirac statistics while properly modeling the finite density of states (DOS) of 2-D semiconductors and graphene. The approach circumvents difficulties that arise in commercial TCAD tools, such as the proper handling of the 2-D DOS and the simulation boundary conditions when the structure terminates with a nonmetallic material. Based on this methodology, we have developed 2dmatstacks , an open-source tool freely available on nanohub.org . Overall, this paper equips researchers to analyze, understand, and predict experimental results in complicated vdW stacks.

© 2018 IEEE. In 2-D van der Waals heterostructures, interactions between atomic layers dramatically change the vibrational properties of the hybrid system and demonstrate several interesting phenomena that are absent in individual materials. In this paper, we have investigated the vibrational properties of the heterostructure between transition metal dichalcogenide (TMD) and hexagonal boron nitride (hBN) on gold film at low- and high-frequency ranges by Raman spectroscopy. Nineteen Raman modes have been observed from the sample, including a new interlayer coupling mode at 28.8 cm-1. Compared to reported experimental results of tungsten disulfide (WS2) on SiO2/Si substrates, the Raman spectrum for WS2 on hBN/Au emerges a blue shift of about 8 cm-1. Furthermore, a remarkable enhancement of Raman intensity can be obtained when tuning hBN thickness in the heterostructure. Through systematic first-principles calculations, numerical simulations, and analytical calculations, we find that the 28.8 cm-1 mode originates from the shearing motion between monolayer TMD and hBN layers. In addition, the gold substrate and hBN layers form an optical cavity and the cavity interference effects enhance the obtained Raman intensity. This paper demonstrates the novel vibrational modes of 2-D van der Waals heterostructure as an effective tool to characterize a variety of such heterostructures and reveals a new method to enhance the Raman response of 2-D materials.

Vertically aligned carbon nanotubes (VACNTs) have been explored widely in various applications due to their unique anisotropic properties. However, its application is limited due to large aspect ratio of nanotubes which lead to buckling phenomena. In this paper, we perform a finite element analysis to predict the variation of elastic modulus and critical buckling load of VACNTs. While elastic modulus is obtained from the slope of stress–strain variation of tubes when one end is fixed and another end is subjected to longitudinal loading, critical buckling load is found using eigenvalue analysis corresponding to first buckling mode. We also perform study to show size dependence of elastic modulus and buckling load of single walled carbon nanotubes (SWCNTs) using FEM approach and compare the results with MD results found in the literature. After validating FEM approach with available results of single-walled and double-walled carbon nanotubes, we apply the same method to arrays of VACNTs. It is found that elastic modulus of VACNTs increases from 1.18 TPa to 2.02 TPa when the size increases from 4 to 36 tubes and then it becomes nearly size independent. The variations of critical buckling load versus other parameters such as tube diameter, intertube spacing, etc., are also obtained. It is found that with the increase in diameter, there is a steep rise in the buckling load for the case of VACNTs arrays. In order to show the influence of non-linear van der Waals force in VACNTs, we compare the above results with and without the presence of van der Waals force and discuss its significance. The modelling and analysis presented in the paper can be used to optimise the number density of VACNTs for different applications.

International audience; Phosphorus bearing molecules have been discovered in the circumstellar and interstellar media. Modeling their abundance accurately requires computations of rate coefficients induced by collision with He and H 2 (i.e., the most abundant gaseous components). These calculations may be carried out by first determining highly accurate potential energy surface (PES) and cross sections. In this paper, we present the first PES of the CP(X 2 Σ +)-He(1 S) van der Waals collisional complex. The ab initio interaction potential was performed using the explicitly correlated restricted coupled cluster approach with simple, double, and perturbative triple excitation (RCCSD(T)−F12) in connection with the augmented-correlation consistent−polarized valence triple-ζ Gaussian basis set (aug-cc-pVTZ). The potential presents two minima of −18.62 cm −1 and −18.72 cm −1. From the PES obtained, we have computed state-to-state excitation cross sections of CP due to collision with He for energies up to 500 cm −1. Rotational transitions involving the fine-structure levels of the CP molecule were treated with a recoupling technique based on the scattering matrix calculated with the exact quantum mechanical close coupling method. Discussions on the propensity rules between the fine-structure levels were made and we found that the Δj = ΔN transitions are favored with respect to the Δj ≠ ΔN ones. The data presented in this paper may have a great impact on the accurate determination of the CP abundance in space.

Thinning and rupture of a thin film of a power-law fluid on a solid substrate under the balance between destabilizing van der Waals pressure and stabilizing capillary pressure is analysed. In a power-law fluid, viscosity is not constant but is proportional to the deformation rate raised to the $n-1$ power, where $0 is the power-law exponent ($n=1$ for a Newtonian fluid). In the first part of the paper, use is made of the slenderness of the film and the lubrication approximation is applied to the equations of motion to derive a spatially one-dimensional nonlinear evolution equation for film thickness. The variation with time remaining until rupture of the film thickness, the lateral length scale, fluid velocity and viscosity is determined analytically and confirmed by numerical simulations for both line rupture and point rupture. The self-similarity of the numerically computed film profiles in the vicinity of the location where the film thickness is a minimum is demonstrated by rescaling of the transient profiles with the scales deduced from theory. It is then shown that, in contrast to films of Newtonian fluids undergoing rupture for which inertia is always negligible, inertia can become important during thinning of films of power-law fluids in certain situations. The critical conditions for which inertia becomes important and the lubrication approximation is no longer valid are determined analytically. In the second part of the paper, thinning and rupture of thin films of power-law fluids in situations when inertia is important are simulated by solving numerically the spatially two-dimensional, transient Cauchy momentum and continuity equations. It is shown that as such films continue to thin, a change of scaling occurs from a regime in which van der Waals, capillary and viscous forces are important to one where the dominant balance of forces is between van der Waals, capillary and inertial forces while viscous force is negligible.

Purpose This paper aims to investigate the effect of changing speed of the entraining motion on the formation of ultra-thin lubricating films under different elliptical ratios. The ellipticity parameter (K) varied from 1 (a ball-on-plate configuration) to 6 (a configuration approaching line contact). The influence of the ellipticity parameters, the dimensionless speed and the effects of surface forces on the formation of the minimum film thickness has been demonstrated. The demarcation boundary between region dominated by elastohydrodynamic lubrication (EHL) and that by the surface force action has been demonstrated for different elliptical ratios. Design/methodology/approach The numerical solution has been carried out, using the Newton–Raphson iteration technique, applied for the convergence of the hydrodynamic pressure. The film thickness and pressure distribution are obtained by simultaneous solution of the Reynolds’ equation, the elastic deformation (caused by hydrodynamic pressure, surface force of solvation and Van der Waals force) and the load balance equation. The operating conditions, load and speed of entraining motion, promote formation of ultra-thin films that are formed under the combined action of EHL, surface contact force of solvation and molecular interactions due to presence of Van der Waals force. Findings The paper provides insights about the transition between region dominated by EHL and that by the surface force action for changing ellipticity ratio (K) from 1 (a ball-on-plate configuration) to 6 (a configuration approaching line contact). Originality/value This paper fulfils an identified need to study the effect of changing ellipticity ratio on the formation of ultra-thin films that are formed under the combined action of EHL, surface contact force of solvation and molecular interactions due to presence of Van der Waals force.

This paper relates to a computational investigation of nanomechanical properties of graphene spirals. The molecular dynamics simulation method was used to investigate the mechanical properties including the stress–strain and force–strain diagrams under tensile tests as well as the fracture characteristics of the single- and double-layer graphene spirals. The adaptive intermolecular reactive empirical bond order potential was employed to model the covalent bonds and van der Waals interactions between the carbon atoms. Also, in the last section of the paper, the mechanical behavior of the spirals is scrutinized with respect to nitrogen and boron doping with various percentages and the Young’s moduli of the graphene spirals are presented as the functions of size and doping ratios according to the stress–strain diagrams. The results reveal three major deformation phases namely, elastic due to the van der Waals interactions, elastic due to the covalent bonds, and inelastic regimes. According to the results, the graphene spirals have superelastic characteristics in the range of 2000–3000% strains and very high strength values depending on the nanostructure size.

In this paper, the dynamic instability of double-walled carbon nanotubes (DWCNTs) enclosed by an elastic medium under parametric excitation of sequential moving nanoparticles has been analyzed. Using Hamilton’s principle, the governing equations are derived based on the Euler–Bernoulli beam theory. All inertial terms of the moving nanoparticles are taken into account and small-scale effects are applied in the dynamic formulation based on the Eringen’s nonlocal elastic theory. The incremental harmonic balance (IHB) technique is applied to estimate the parametric instability regions of the DWCNT carrying the moving nanoparticles. It is found that the stability of the system could be improved in some cases, such as taking into account the Van der Waals (vdW) effect, reducing the amplitude of axial oscillating force, enlarging the amplitude of the static axial tensile force and enhancing the stiffness of the elastic medium. The accuracy of the presented analyses is examined by comparing the results with those reported in the literature and very good agreement is observed. The results of this paper can be used in the design of advanced nano-electro-mechanical systems (NEMS) and nanodrug delivery systems, in which nanotubes act as the basic elements.

Materials with van der Waals bonding show exotic physics and may have applications in a variety of areas including new optoelectronic devices, spintronic devices, and as quantum materials. To date, control over the morphology and surface orientation of thin films of these materials without substrate pretreatment has been difficult. In this paper, the authors report the growth of Bi2Se3 on GaAs (001) substrates. By controlling the growth conditions and adatom mobility, the authors are able to obtain epitaxial growth in the (0015) orientation without substrate prepatterning. Although the growth window is small, this demonstration opens the door for future control of the orientation of van der Waals materials through control of parameters during growth and via interaction with the substrate. Materials with van der Waals bonding show exotic physics and may have applications in a variety of areas including new optoelectronic devices, spintronic devices, and as quantum materials. To date, control over the morphology and surface orientation of thin films of these materials without substrate pretreatment has been difficult. In this paper, the authors report the growth of Bi2Se3 on GaAs (001) substrates. By controlling the growth conditions and adatom mobility, the authors are able to obtain epitaxial growth in the (0015) orientation without substrate prepatterning. Although the growth window is small, this demonstration opens the door for future control of the orientation of van der Waals materials through control of parameters during growth and via interaction with the substrate.

A multiplication error led to incorrect values of C2e and C1o in Table 1 of the above paper. The correct table is given below. All numerical results, graphs, and conclusions of the paper remain unchanged. &#13.

Three-dimensional topological insulators (TIs) are a new class of quantum materials that have insulating energy gaps in bulk form but exhibit robust gapless surface states protected by time-reversal symmetry. It was theoretically predicted and experimentally confirmed that the binary tetradymites $\mathrm{B}{\mathrm{i}}_{2}\mathrm{T}{\mathrm{e}}_{3}$, $\mathrm{B}{\mathrm{i}}_{2}\mathrm{S}{\mathrm{e}}_{3}$, and $\mathrm{S}{\mathrm{b}}_{2}\mathrm{T}{\mathrm{e}}_{3}$ are all TIs, while the fourth system out of the 2 \ifmmode\times\else\texttimes\fi{} 2 combination, $\mathrm{S}{\mathrm{b}}_{2}\mathrm{S}{\mathrm{e}}_{3}$, was prevailingly believed to be topologically trivial due to its relatively weak spin-orbit coupling (SOC). In this paper, we demonstrate through a comparative first-principles study that $\mathrm{S}{\mathrm{b}}_{2}\mathrm{S}{\mathrm{e}}_{3}$ is actually also an intrinsic TI, as characterized by its topologically protected surface states and ${Z}_{2}$ invariant. The underlying reason is the inclusion of the ubiquitous van der Waals attraction between the quintuple layers, effectively narrowing the bulk band gap, allowing the SOC effect to induce a band inversion around the Fermi level. This paper also points to the importance of the seemingly weak dispersion forces in defining the topological properties of quantum materials.

In this paper, we consider an unusual connection between different fluids. Having established a research goal we would like to consider a toy model of the Universe and investigate its behavior, especially for later time evolution for well known facts. The main goal of the article is to consider a toy model of the Universe with generalized ghost dark energy, Van der Waals gas and a phenomenologically modified fluid. The origin of the last component can be understood as a result of interaction between some original fluid and some source of energy or matter in Universe. By unusual connection we mean an assumption that generalized ghost dark energy has its contribution to the model by an interaction term Q and we suppose an interaction of the form Q=3H b(ρ t o t −ρ G D e ). Graphical analysis is performed and the questions of validity of the generalized second law of thermodynamics and stability of the model also approached in this paper.

This paper presented a method for multiwalled carbon nanotube(MWCNT) and graphene fusion by applying current to the electric circuit system inside scanning electron microscopy (SEM). The MWCNT was picked up from CNT bulk and the graphene flake was exfoliated from graphite by nanorobotics manipulation system. The current was applied to the two ends of carbon nanotube and graphene. The C-C bonds at the end of the CNT and graphene were fused together. The theoretical tensile force and van der Waals force were about 166 nN and 30 nN. The method of this paper presented that the tensile force was about 20 nN before fusing the MWCNT and graphene. In contrast, the tensile force of fused carbon nanotube and graphene was about 90 nN and it was four times of the previous force.

Two-dimensional van der Waals materials have attracted considerable attention because of their promising applications in spintronic devices. This paper reports on first-principles calculations of the electronic structure and ferromagnetism of Cr 2 Ge 2 Te 6 with surface Ge vacancies. These vacancies are found to remove the bandgap and induce metallicity in Cr 2 Ge 2 Te 6 that persists with decreasing Ge-vacancy concentration. Meanwhile, the Ge vacancies cause an unexpected sharp increase in the magnetic anisotropy energy compared to that of perfect Cr 2 Ge 2 Te 6. More importantly, how thickness affects the magnetic anisotropy energy is studied to show that the latter oscillates upon increasing the number of layers, thereby switching between the out-of-plane and in-plane magnetization directions. The present findings regarding a surface-vacancy-tuned bandgap and magnetism controlled by the layer thickness in a two-dimensional van der Waals magnet could lead to potential applications in next-generation magnetic memory storage, sensors, and spintronics.Two-dimensional van der Waals materials have attracted considerable attention because of their promising applications in spintronic devices. This paper reports on first-principles calculations of the electronic structure and ferromagnetism of Cr 2 Ge 2 Te 6 with surface Ge vacancies. These vacancies are found to remove the bandgap and induce metallicity in Cr 2 Ge 2 Te 6 that persists with decreasing Ge-vacancy concentration. Meanwhile, the Ge vacancies cause an unexpected sharp increase in the magnetic anisotropy energy compared to that of perfect Cr 2 Ge 2 Te 6. More importantly, how thickness affects the magnetic anisotropy energy is studied to show that the latter oscillates upon increasing the number of layers, thereby switching between the out-of-plane and in-plane magnetization directions. The present findings regarding a surface-vacancy-tuned bandgap and magnetism controlled by the layer thickness in a two-dimensional van der Waals magnet could lead to potential application...

In this paper, we study the collision of a one-dimensional steepened wave with a blast wave for the system of partial equations describing the unsteady flow of dusty real reacting gases with the same γ-law. The real gas is characterized by a van der Waals type equation of state. Special attention is devoted to analyzing the effects of real, reaction, and dusty gas parameters on the steepened wave. The amplitudes of the reflected and/or transmitted waves along with the jump in shock acceleration after the interaction are also obtained.In this paper, we study the collision of a one-dimensional steepened wave with a blast wave for the system of partial equations describing the unsteady flow of dusty real reacting gases with the same γ-law. The real gas is characterized by a van der Waals type equation of state. Special attention is devoted to analyzing the effects of real, reaction, and dusty gas parameters on the steepened wave. The amplitudes of the reflected and/or transmitted waves along with the jump in shock acceleration after the interaction are also obtained.

The content of this paper includes studying holographical and thermodynamical aspects of dyonic black holes in the presence of massive gravity. For the first part of paper, thermodynamical properties of the bulk which includes black holes are studied and the main focus is on critical behavior. It will be shown that the existence of massive gravitons introduces remnant for temperature after evaporation of black holes, van der Waals phase transition for non-spherical black holes and etc. The consistency of different thermodynamical approaches toward critical behavior of the black holes is presented and the physical properties near the region of thermal instability are given. Next part of the paper studies holographical aspects of the boundary theory. Magnetization and susceptibility of the boundary are extracted and the conditions for having diamagnetic and paramagnetic behaviors are investigated. It will be shown that generalization to massive gravity results into the existence of diamagnetic/paramagnetic phases in phase structure of the hyperbolic and horizon flat of boundary conformal field theory. © 2017 by WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim, Research Institute for Astronomy and Astrophysics of Maragha

The layered van der Waals (vdW) heterostructure, assembled from monolayer graphene, hexagonal boron nitride (h-BN) and other atomic crystals in various combinations, is emerging as a new paradigm with which to attain desired electronic and optical properties. In this paper, we study theoretically the mid-infrared optical properties of the vdW heterostructure based on the graphene–h-BN system. The light–matter interaction of this heterostructure system is described by the hyperbolic phonon–plasmon polaritons which originate from the coupling modes of surface plasmon polaritons (SPPs) in graphene with hyperbolic phonon polaritons (HPPs) in h-BN. By numerical simulation, we find that the coupling modes are governed by the Fermi level of monolayer graphene, the thickness of the h-BN slab and the mode excitation sequence of SPPs and HPPs. Moreover, the response of the coupling modes of the graphene–h-BN heterostructure on a noble metal layer is also proposed in this paper.

Various models were proposed to calculate the van der Waals (vdW) forces, but they have generally been complicated and time-consuming. In this paper, a spherical volume elements scheme to calculating the vdW force distributions is proposed, on the basis of the infinitesimal dividing modeling scheme. We apply this scheme to calculate the vdW force distributions between sphere and three types of surfaces with different roughness and also to irregular particles (cylinders, circular cone) orientated differently with respect to the surface. The simulation results reveal that the surface with low roughness has the narrowest force distributions. The average force for the circular cone bottom case is 1, 2, 37 times higher than the case of horizontal, vertical cylinder and circular cone top, respectively. The calculated force distributions are good agreement with exist experimental data. By defining the effective zones of both particles and surface, the computational time of the scheme is an order of magnitude faster than the case of considering the whole surface. The proposed model established the effective zone of the particles in contact from a completely new perspective and significantly simplifies the process of force evaluation.

In this paper, Hamiltonian approach for solving vibration in the first approximation is extended into a high order Hamiltonian approach method for n order approximation. The method is applied for computation of the frequency of doubly clamped beam type N/MEMS subjected to the van der Waals attraction and the Duffing oscillator with seventh order nonlinearity. The obtained results are compared with numerically and other analytically obtained results. It is concluded that the solution in the third approximation gives the most appropriate solution in comparison to other analytical methods. The time history diagrams and the phase plane diagrams calculated analytically are on the top of the curves obtained numerically.

International audience; Encapsulation of photoactive organic molecules inside single-walled carbon nanotubes (SWNTs) appears to be of great interest in terms of high power conversion efficiency and long-term stability for a commercial application of organic solar cells (OSCs). In this paper, we report a charge transfer (CT) evidence in donor–acceptor SWNTs filled with Sexithiophene oligomers (6T) by Raman spectroscopy. To compute the optimal diameter and demonstrate the most stable structure of the hybrid systems with either a single 6T molecule encapsulated into SWNTs (6T@SWNTs), or two 6T chains encapsulated (6T-6T@SWNTs), we have performed structural geometry optimization on the hybrid encapsulated systems using a convenient Lennard–Jones (LJ) expression of the van der Waals (vdW) intermolecular potential. Combining the density functional theory (DFT), molecular mechanics, bond polarizability model, and the spectral moment method (SMM), we computed the polarized nonresonant Raman spectra of 6T molecule and SWNTs (metallic and semiconducting) before and after encapsulation. The influence of the encapsulation on the Raman-active modes of the 6T molecule and those of the nanotube (radial breathing modes and tangential modes) are analyzed. In particular, significant changes observed in the G-band wavenumber. The possibility (or not) of an eventual CT between the 6T oligomer and the nanotube in both hybrid systems (6T@SWNTs and 6T-6T@SWNTs) is discussed. We show that there is a dependence of the CT with respect to the diameter of SWNTs, the CT vanish with increasing diameter of the nanotubes. Our finding of CT behavior in the filled SWNTs with respect to SWNT diameter will provide a useful guidance for enhancing the performance of OSCs by SWNTs.

The speed and angular distribution of O atoms arising from the photofragmentation of C(5)H(8)-O(2), the isoprene-oxygen van der Waals complex, in the wavelength region of 213-277 nm has been studied with the use of a two-color dissociation-probe method and the velocity map imaging technique. Dramatic enhancement in the O atoms photo-generation cross section in comparison with the photodissociation of individual O(2) molecules has been observed. Velocity map images of these "enhanced" O atoms consisted of five channels, different in their kinetic energy, angular distribution, and wavelength dependence. Three channels are deduced to be due to the one-quantum excitation of the C(5)H(8)-O(2) complex into the perturbed Herzberg III state ((3)Δ(u)) of O(2). This excitation results in the prompt dissociation of the complex giving rise to products C(5)H(8)+O+O when the energy of exciting quantum is higher than the complex photodissociation threshold, which is found to be 41740 ± 200 cm(-1) (239.6±1.2 nm). This last threshold corresponds to the photodissociation giving rise to an unexcited isoprene molecule. The second channel, with threshold shifted to the blue by 1480 ± 280 cm(-1), corresponds to dissociation with formation of rovibrationally excited isoprene. A third channel was observed at wavelengths up to 243 nm with excitation below the upper photodissociation threshold. This channel is attributed to dissociation with the formation of a bound O atom C(5)H(8)-O(2) + hv → C(5)H(8)-O(2)((3)Δ(u)) → C(5)H(8)O + O and/or to dissociation of O(2) with borrowing of the lacking energy from incompletely cooled complex internal degrees of freedom C(5)H(8)*-O(2) + hv → C(5)H(8)*-O(2)((3)Δ(u)) → C(5)H(8) + O + O. The kinetic energy of the O atoms arising in two other observed channels corresponds to O atoms produced by photodissociation of molecular oxygen in the excited a (1)Δ(g) and b (1)Σ(g)(+) singlet states as the precursors. This indicates the formation of singlet oxygen O(2)(a (1)Δ(g)) and O(2)(b (1)Σ(g)(+)) after excitation of the C(5)H(8)-O(2) complex. Cooperative excitation of the complex with a simultaneous change of the spin of both partners (1)X-(3)O(2) + hν → (3)X-(1)O(2) → (3)X + (1)O(2) is suggested as a source of singlet oxygen O(2)(a (1)Δ(g)) and O(2)(b (1)Σ(g)(+)). This cooperative excitation is in agreement with little or no vibrational excitation of O(2)(a (1)Δ(g)), produced from the C(5)H(8)-O(2) complex as studied in the current paper as well as from the C(3)H(6)-O(2) and CH(3)I-O(2) complexes reported in our previous paper [Baklanov et al., J. Chem. Phys. 126, 124316 (2007)]. The formation of O(2)(a (1)Δ(g)) from C(5)H(8)-O(2) was observed at λ(pump) = 213-277 nm with the yield going down towards the long wavelength edge of this interval. This spectral profile is interpreted as the red-side wing of the band of a cooperative transition (1)X-(3)O(2) + hν → (3)X(T(2))-(1)O(2)(a (1)Δ(g)) in the C(5)H(8)-O(2) complex.

In this paper, we have considered a very general van der Waals equation of state to study the one-dimensional motion of magnetogasdynamic (MGD) equations. Transport equations for the discontinuity waves are obtained and studied in detail. The effect of van der Waals excluded volume and the intermolecular force of attraction on the evolution of these waves is studied. Explicit expressions for the jump in the mass density and the magnetic pressure are obtained and analyzed in detail. Finally, the interaction of the weak discontinuity with the characteristic shock is studied and the amplitudes of the reflected and the transmitted waves are obtained.

Most recently, the whole world is struggling against the virulent pandemic COVID-19. Due to the unbounded global spread of the disease, having biosensors with high performance such as high sensitivity and accuracy is of utmost importance. In this paper, the effects of various parameters on the behaviors of micro-biosensors are investigated in order to enhance their performance. These parameters are related to the geometry and material, and they are assumed to be gradually changing in the longitudinal direction of the biosensor according to a power law. Therefore, they are called functionally graded geometrical and material parameters. Another aspect is when considering microcantilever-based biosensors, the main behavior parameter is the deflection at the free end. In the analyses, the influences of the surface stress and van der Waals intermolecular forces are taken into account. Also, the total energy of the beam, which is the combination of the van der Waals energy and the elastic strain energy, is accomplished. In addition, the equivalent force causing the deflection is also evaluated using Castigliano method for two cases. These cases account for a concentrated force at the free end and a distributed load along the biosensor, respectively. Since the governing equations account for the size dependency and the considered parameters are functions of the position, the solution is too complex to be achieved analytically, and therefore, numerical methods are applied. For uniform biosensors made of homogeneous materials, or in other words when all parameters are not varying with the position, the obtained results are compared with those in the literature, and good agreement is obtained. On the other hand, the performance, which include sensitivity and limit of detection, of functionally graded biosensors can be enhanced by proper choices of the considered parameters and the corresponding exponent of the gradation function.

In this paper, the surface theory and compatibility conditions are used to describe the behavior of wave propagation and their culmination into a shock wave in a non-ideal reacting gas with dust particles. The one-dimensional steepening of waves is considered. A Bernoulli-type transport equation for the velocity gradient is obtained. A numerical approach is used to explain the effects of van der Waals excluded volume of the medium, radiation parameter, ratio of specific heats and dust particles.

In this paper, the bound states of pentaquark systems are studied by solving the Schrodinger equation containing Van der Waals potential via Nikiforov–Uvarov method. The binding energies, wave functions and the masses of heavy pentaquarks are calculated. The results are in agreement with the existing ones in the literature.

The discovery of two-dimensional (2D) materials like graphene inspired the researchers and scientists to develop new 2D materials. The 2D materials create extensive attention due to their novel electronic properties, large surface area, charging capacity, optical, biocompatible, unique physical and chemical properties. Many of these properties are an excellent requirement for an application of electrode for batteries and super-capacitors. The applications of 2D materials are not just confined to Opto and nano-electronics but a strong potential in gas, and biosensing technologies. The 2D materials are stackable through weak Van der Waals, therefore, used in alkali metal ion batteries as electrodes, this causes zero volume and area changes during the intercalation and deintercalation of alkali metal. Also, a large surface of 2D materials provides large storage capacity as compared to the bulk materials. The heterostructures based on 2D materials pay significant attention towards the optoelectronics, nanoelectronics and in alkali metal ion battery applications also. In this paper, we review the importance of heterostructure, stacking technique in interfacial synthesis, address their structural morphologies by the interface of 2D materials and its application for energy storage, gas, and biosensing applications. We will come up with an overview of interfacial characters and highlights about the advantages and individuality of 2D materials.

The fundamental ideas for a non-local density functional theory -- capable of reliably capturing van der Waals interaction -- were already conceived in the 1990's. In 2004, a seminal paper introduced the first practical non-local exchange-correlation functional called vdW-DF, which has become widely successful and laid the foundation for much further research. However, since then, the functional form of vdW-DF has remained unchanged. Several successful modifications paired the original functional with different (local) exchange functionals to improve performance and the successor vdW-DF2 also updated one internal parameter. Bringing together different insights from almost two decades of development and testing, we present the next-generation non-local correlation functional called vdW-DF3, in which we change the functional form while staying true to the original design philosophy. Although many popular functionals show good performance around the binding separation of van der Waals complexes, they often result in significant errors at larger separations. With vdW-DF3, we address this problem by taking advantage of a recently uncovered and largely unconstrained degree of freedom within the vdW-DF framework that can be constrained through empirical input, making our functional semi-empirical. For two different parameterizations, we benchmark vdW-DF3 against a large set of well-studied test cases and compare our results with the most popular functionals, finding good performance in general for a wide array of systems and a significant improvement in accuracy at larger separations. Finally, we discuss the achievable performance within the current vdW-DF framework, the flexibility in functional design offered by vdW-DF3, as well as possible future directions for non-local van der Waals density functional theory.

The rupture of thin liquid films driven by the van der Waals force is of significance in many engineering processes, and most previous studies have relied on the lubrication approximation. In this paper, we develop a smoothed particle hydrodynamics (SPH) representation for the van der Waals force and simulate the rupture of thin liquid films without resort to lubrication theory. The van der Waals force in SPH is only imposed on one layer, i.e., the outermost layer of fluid particles, where a weighting function is deployed to evaluate the contributions of particles on or near the interface. However, to obtain an accurate hydrostatic pressure in reaction to the van der Waals force, a smaller smoothing length is used for the calculation of the weighting function than that used for SPH discretizations of the bulk fluid. The same surface particles are also used to model the surface tension. To deal with the rupture of a thin liquid film with a very small aspect ratio e (e = thickness/length), a coordinate transformation is introduced to shrink the length of the liquid film to achieve accurate numerical resolution with a manageable number of particles. As verifications of our physical model and numerical algorithm, we simulate the hydrostatic pressure in a stationary film and the relaxation of an initially square droplet and compare the SPH results with the analytical solutions. The method is then applied to simulate the rupture of thin liquid films with moderate and small aspect ratios (e = 0.5 and 0.005). The convergence of the method is verified by refining particle spacing to four different levels. The effect of the capillary number on the rupture process is analyzed.

In this paper, the effect of surface roughness on the pull-in behavior of beam-type nano-actuator in the presence of intermolecular Van der Waals force has been investigated. In order to model the surface roughness, the roughness has been modeled as a step on the fixed electrode. Based on the modified couple stress theory and by using Hamilton’s principle, the governing equation and boundary conditions have been derived for the Euler–Bernoulli beam model. The differential quadrature method has been used to solve the nonlinear governing equations of the system. The results showed that the presence of roughness on the fixed electrode leads to an increase in the displacement of the beam and a reduction in the pull-in voltage, especially when the roughness is at the end of the beam and has considerable height. In this case, the freestanding behavior of the nano-actuator and the effect of roughness on the critical intermolecular force in the absence of electrostatic force are also evaluated. The results revealed a decrease in the critical intermolecular force due to the presence of roughness. However, increasing the material length scale parameters leads to an increase in the pull-in voltage and the freestanding values. Also, the size effect parameter decreases the displacement at the end of the beam.

Explicit solutions are derived to study the equilibrium distance as well as potential energy between graphene and its derivative forms. Since the application of explicitly analytical solutions is limited to homogenous deformation and cannot capture the edge effect, Gaussian quadrature is presented to overcome these problems. The two key elements, i.e., truncation distance and the size of integration element, which are closely related to the computational efficiency and accuracy have been systemically studied. Fitting functions in terms of the above-mentioned two key elements are also provided to easily evaluate the difference of Gaussian quadrature. This paper provides a good understanding of the van der Waals interaction between graphitic nanostructures, and should be of great help for fabricating nano devices and simulating their mechanical behaviors such as spontaneous buckling.

Iodine oxide (IO) is an important tropospheric molecule. In the present paper, we mapped the potential energy surfaces (PESs) of the doubly degenerate IO(X-2 pi)-Ar van der Waals system using single- and double-excitation coupled cluster approaches with non-iterative perturbation treatment of triple excitations [RCCSD(T)] extrapolated to the complete basis set (CBS) limit. In addition to bent local minima, we identified a linear Ar-IO complex as a global minimum. Afterwards, we performed scattering calculations on these PESs, considering the non-zero spin-orbit contribution and the Renner-Teller effect. The integral cross-sections exhibit an oscillatory structure vs. the final rotational state, as already observed for the NO(X-2 pi)-Ar system. Moreover, computations reveal that the Ar-IO complex is stable toward dissociation into IO and Ar. Therefore, it can be found in the atmosphere and participates in iodine compound physical chemical processes occurring there.

Detection of the antiferromagnetic (AFM) state is an important issue for the application of two-dimensional (2D) antiferromagnets in spintronics, and interfacial exchange coupling is a highly efficient means to detect AFM order. However, there are no experimental reports of AFM state detection in van der Waals heterostructures, based on which 2D AFM spintronics can be developed. In this paper, we report a spin flop transition (SFT)-induced anomalous Hall effect in a heterostructure of MnPS3/graphite flake (GF) through van der Waals proximity coupling. The scaling behavior study and theoretical calculations confirm that the SFT in AFM MnPS3 can generate momentum-space nonzero Berry curvature integration in the adjacent GF. Our work opens a path for the realization of AFM state detection through the proximity effect in a stacking structure, thereby promoting the application of 2D antiferromagnets in future 2D spintronics.

In the present work, rheological behaviors of fresh cement paste are studied based on multi-disciplinary approaches, i.e., colloidal suspension using attractive van der Waals force, rheology using the Bingham model and Bingham–Papanastasiou model, which are able to describe the behavior of cement pastes before and after yield stress, and finally the continuum mechanics based on Maxwell and Kelvin–Voigt models. To achieve this, the fresh cement paste with different water-to-cement ratios of 0.3 up to 0.6 is prepared. The attractive van der Waals forces are estimated based on the distances between solid cement particles, which vary at every single water-to-cement ratio. The rheology experiments of all water-to-cement ratios are performed using a rheometer. According to our experimental outcomes, the Bingham and Bingham–Papanastasiou models are applied in the modeling of the experimental curves and determination of yield stress and viscosity. Maxwell and the Kelvin–Voigt models are utilized in describing solid-like behavior before yield stress and fluid-like behavior beyond yield stress. It is observed that the increase of water generates a decrease in the viscosity, yield stress, and packing concentration of solids. It also increases the distances between two cement particles in the cement pastes. According to the modeling results, the Bingham–Papanastasiou model is well adapted for the cement paste flow due to its additional modeling parameter, which is known as m. The role of m is understood and described by linking the van der Waals interaction, rheology, and three-element Kelvin–Voigt model as a whole in function of water-to-cement ratio. m is understood as a key parameter in which the distance between particles affects the rheological behavior of fresh cement pastes. Lastly, the two-phase flow simulations have been successfully achieved and compared with the experiments. The conclusion and outlooks are summarized and discussed at the end of the paper.

Interlayer twisting in two-dimensional (2D) van der Waals (vdW) heterostructures often leads to a periodic moire pattern which is a superlattice structure on top of the original atomic lattice of the 2D layers. The formation of a moire superlattice can be accompanied by a significant structural reconstruction and ultra-flat electronic bands. The moire superlattice is typically built with a tunable scale by controlling the rotation angle θ between the individual 2D layers. In this paper, we report the structural reconstruction and electronic transition in moire patterns of twisted bilayer antimonene, based on Kohn–Sham density functional theory calculations. Starting from rigid moire structures, the atomic relaxation leads to an array of high-symmetry stacking domains with soliton boundaries through a vortex-like reconstruction. For twist angle θ ≤ 6.01°, the impact of the structural reconstruction on the electronic bands becomes very significant, in the appearance of flat bands at the valence band edge, and no magic angle is required for the flat bands to appear in the 2D Sb moire patterns. Both inhomogeneous interlayer hybridization and local strain are found to be responsible for the formation of these flat electronic bands.

Two-dimensional (2D) layered III-VI semiconductors such as GaSe have attracted a lot of attention in recent years. Bulk GaSe consists of stacks of layers held together by weak interlayer interaction generally assumed to be of van der Waals type. However, proper justification of this assumption has been lacking in the reported studies. In this paper, we explore in detail the interlayer coupling in GaSe by studying lattice dynamics using first-principles density functional theory. Our study strongly suggests that contrary to common assumption, the contribution of Coulomb interaction in interlayer coupling can be significantly higher than that of van der Waals interaction in GaSe and other similar 2D layered semiconductors. The suggested predominance of electrostatic over van der Waals interaction in interlayer coupling may have important implications for various physical properties of GaSe and related layered semiconductors. Further, we study polarized Raman spectra, infrared (IR) activities, mode symmetry assignments, and Born-effective charge tensors for bulk GaSe polytypes (β, ϵ, γ). The Raman mode intensities are calculated for different light polarization setups and signature Raman and IR active modes are identified for each GaSe polytype (structure). In addition, the influence of film thickness and strain on Raman and IR mode frequencies and intensities of GaSe are explored and compared with available experiments.

In a previous paper (http://www.phys.uri.edu/people/nightingale/publications.html, chem-ph/9406003) we developed a form of variational trial wave function and applied it to van der Waals clusters: five or less atoms of Ar and Ne modeled by the Lennard-Jones potential. In addition, we tested the trial functions for a hypothetical, light atom resembling Ne but with only half its mass. We did not study atoms such as He with larger de Boer parameters, i.e., systems in which the zero point energy plays a more important role relative to the potential energy. This is the main purpose of the present paper. In fact, we study clusters to the very limit where the zero-point energy destroys the ground state as a bound state. A simple picture of this un-binding transition predicts the power law with which the energy vanishes as the de Boer parameter approaches its critical value and the power of the divergence of the the size of the clusters in this limit. Our numerical results are in agreement with these predictions., Comment: text and figures TeX form, 4 pages

In this paper, we systematically investigate the structural and electronic properties of Janus transition metal dichalcogenide bilayers using first-principles calculations. 2H phase Janus MXY (M = Mo, W; X, Y=S, Se, Te) bilayers with five possible stacking types are focused. The energetically favorable stacking type and the corresponding gap between layers are determined by comparing binding energies with van der Waals interaction. The Janus MXY bilayers with this specific stacking are indirect semiconductors with bandgaps ranging from 0.014 eV to 0.932 eV, which are smaller compared with their monolayers. The valence band maximums of MoSeTe, WSSe and WSeTe bilayers locate at high-symmetry K point while the conduction band minimums of all bilayers except MoSSe move to the position between K and Γ. Moreover, the electronic band structures of total 30 possible Janus TMD bilayers are demonstrated, presenting a promising platform for nanoscale electronic and optoelectronic devices.

Purpose – This paper aims to assess the accuracy of Lattice Boltzmann method (LBM) for numerical simulation of the stratification of a Van der Waals (VdW) fluid subjected to a gravity field and non-uniform temperature distribution. A sensitivity analysis of the influence of the pseudopotential parameters and the grid resolution is presented. The effect of gravity force on interface densities, density profiles and liquid volume fraction is studied. Design/methodology/approach – The D2Q9 multiple-relaxation-time pseudopotential LBM for two-phase flow is proposed to simulate the phase separation. The analytical solution for density profiles in a one-dimensional problem is derived and used as a benchmark case to validate the numerical results. Findings – The numerical results reproduce the analytical density profiles with great accuracy over a wide range of simulation conditions, including variations of the gravity and temperature fields. Particularly, the numerical simulations are able to represent the effect of gravity on the existence and position of the liquid– vapor boundary of an ideal pure substance in thermodynamic equilibrium. The sensitivity of the results to variations of the calibration parameters of the VdW pseudopotential was assessed. Research limitations/implications – The numerical simulations were performed assuming a VdW fluid in a 2-D cavity with one periodic direction for which analytical solutions for benchmarking purposes are possible to obtain. Originality/value – The following fundamental question is addressed: Is the pseudopotential LBM capable of simulating accurately the liquid–vapor equilibrium under gravity forces and temperature gradients? Moreover, regarding that the pseudopotential model requires the calibration of several internal parameters to achieve thermodynamic consistency, the sensitivity of the results to variations of these parameters is assessed. Fil: Fogliatto, Ezequiel Oscar. Comisión Nacional de Energía Atómica. Gerencia del Área de Energía Nuclear. Instituto Balseiro; Argentina Fil: Clausse, Alejandro. Comisión Nacional de Energía Atómica; Argentina. Universidad Nacional del Centro de la Provincia de Buenos Aires. Facultad de Ciencias Exactas. Grupo de Plasmas Densos Magnetizados. Provincia de Buenos Aires. Gobernación. Comision de Investigaciones Científicas. Grupo de Plasmas Densos Magnetizados; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tandil; Argentina Fil: Teruel, Federico Eduardo. Comisión Nacional de Energía Atómica. Gerencia del Área de Energía Nuclear. Instituto Balseiro; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina

In this paper, we develop a coarse grained numerical model for the simulation of a self-organization process for a system of carbon nanotubes under the applied electric field. The model describes the polarization of nanotubes in the system with an electric field and also includes the Van der Waals interaction between nanotubes. We develop an iterative computation algorithm for particle charges in the nanotube, providing a significant speedup of the computation. Another advantage of this algorithm is the better scaling of the computation time as a function of the system size. The results of the application of this model to computing the self-organization process of the dynamics of carbon nanotubes are demonstrated.

Making a nanoparticle (NP) approach and interact with a plasma membrane (PM) through the receptor-ligand interaction is key for applications like targeted drug delivery, cellular imaging, and theranostics. In this paper, we show that the van der Waals (vdW) interactions dominate the electrostatics ensuring that a gold NP approached the PM more spontaneously as compared to a silica NP. The negative σ (charge density) of a PM induces a negative electrostatic potential at the surface of the approaching gold NP and the silica NP; however, there is very little difference between these induced values due to a small electric double layer at the physiological salt concentration (c∞). Hence there is very little difference in the electrostatic repulsion between the two cases, while the PM-NP vdW attraction is much more for the gold NP as a result of a larger Hamaker constant. Therefore, in comparison to the gold NP, the silica NP would (a) undergo a promotion of the specific adhesion and a prevention of the non-specific adhesion simultaneously for a larger σ − c∞ phase space including the physiological conditions, (b) necessitate a larger length of the ligands to trigger spontaneous receptor-ligand interactions, and (c) require a larger driving force for force-driven receptor-ligand interactions.

Future development of spintronic devices urgently requires an advanced control method of spin current. Combining graphene with other various characteristic two-dimensional crystals in different ways can produce a new class of functional materials, which offers a unique platform for spintronics. A specific van der Waals heterostructure consisting of graphene and hexagonal boron nitride (h-BN) as the barrier layer in magnetic tunnel junctions (MTJs) is proposed in this paper. This heterostructure device combines the strong spin filtering effect of graphene/ferromagnet interface and the resonant tunneling effect of graphene/h-BN/graphene van der Waals heterostructure. We demonstrate an effective approach to control spin current based on the bias tunability of the spin resonance tunneling transport. Theoretical research unambiguously reveals that spin resonance appears when the electronic spectra of spin electron in two graphene layers are aligned, which results in a large magnetoresistance and negative differential resistance in the device. The efficient bias controllability of spin current, combined with the excellent magnetoresistance behavior, can be the key building blocks in future spin-based magnetic detection and high-frequency logic devices.

In this paper, we show that MoS2 multilayers have mechanical and electrical properties that qualify them as promising channel materials for an n-type piezoelectric FET (PZ-FET). We present extensive density functional theory calculations to investigate the effects of a compressive, out-of-plane stress on MoS2 monolayers and multilayers and extract the corresponding stiffness, as well as the sensitivity to stress of the conduction and valence band edge, and of the effective masses. Then, we use these material properties and a top-of-the-barrier ballistic transistor model to evaluate numerically the ${I}_{\textsf {DS}}$ versus ${V}_{\textsf {G}}$ characteristics of n-type PZ-FETs with an MoS2 channel material. Our results indicate that MoS2 multilayers are the best material option for n-type PZ-FETs, which can reach a subthreshold swing of about 40 mV/decade for a 5-nm-thick piezoelectric layer. This is because the weak interlayer van der Waals bonding makes the conduction band edge in MoS2 multilayers very sensitive to vertical compressive stress. The simulated MoS2 PZ-FETs exhibit large ${I}_{ \mathrm{\scriptscriptstyle ON}}/{I}_{ \mathrm{\scriptscriptstyle OFF}}$ ratios at low voltage and have better subthreshold steepness compared with the counterpart device employing a 3-D semiconductor.

2D van der Waals chalcogenides such as topological insulators and transition-metal dichalcogenides and their heterostructures are now at the forefront of semiconductor research. In this paper, we discuss the fundamental features and advantages of van der Waals bonded superlattices over conventional superlattices made of 3D materials and describe in more detail one practical example, namely, interfacial phase change memory based on GeTe–Sb2Te3 superlattice structures.

This paper aims to show the characteristics of ultra-thin films for non-Newtonian fluid using Ree-Eyring model where intermolecular forces of solvation and Van der Waal's are considered in addition to the hydrodynamic action to fulfill an identified need for such a conjunction. In this case, the film thickness and pressure distribution are obtained by simultaneous solution of the modified Reynolds’ equation incorporating the effect of non-Newtonian fluid, film thickness equation including elastic deformation caused by all contributing pressures and the load balance equation using Newton-Raphson method with Gauss-Seidel iterations. Effect of changing the operating conditions of speed, load, Eyring shear stress and slide-roll ratio on the characteristic of the contact has been studied. The results show that, for the case where the hydrodynamic action is the only pressure acting to support the applied load capacity, the film thickness and the pressure gradient at the exit of the contact obtained using non-Newtonian model is different than that formed using the Newtonian model especially for the increased value of slide-roll ratio. The main results of this study are that for ultra-thin film, the film thickness formed using non-Newtonian model is smaller compared to that obtained using Newtonian case and the discretization of the film thickness as the gap is reduced occurs similar to the results obtained using Newtonian model. The pressure shape shows no difference compared to that formed using the Newtonian case in which an oscillation around the Hertizan contact pressure shape due to the solvation effect appears. The results also show that for ultra-thin film, changing the Eyring shear stress does not affect the film thickness formation.

The use of higher vibration modes and different geometries of the atomic force microscopy (AFM) piezoelectric micro cantilever (MC) is affected by the surface topography quality in a liquid medium. Therefore, utilizing an appropriate MC geometry and vibration mode is of a great importance. This paper analyzes the effect of different types of AFM MCs on the surface topography quality in the noncontact and tapping modes in a liquid medium. The modified couple stress theory (MCS) in a liquid based on the Timoshenko beam theory is used in order to enhance the accuracy of MC dynamic modeling. In addition, the differential quadrature (DQ) method has been used to discrete the equations. Identification of environmental forces helps to measure the accurate MC vibration amplitude. Investigating the effect of geometric and force parameters on the MC vibration behavior leads to understanding the system to design it properly in a liquid medium. Based on the advanced dynamic modeling, the best MC geometry for the specific surface roughness has been determined in the liquid for the surface topography. Also, due to oscillating the MC near the sample surface, the effect of interaction forces between the sample surface and the MC, including van der Waals, contact and squeeze forces is analyzed in a liquid medium in addition to the hydrodynamic forces. Furthermore, due to the reduction of the MC amplitude caused by the squeeze force; the MC is angled in proportion to the horizontal surface.

Impact of adhesive particles with a wall occurs in many applications, over a wide range of impact speeds. Prediction of whether or not an impacting particle will stick to the wall, and if not prediction of the rebound velocity of the particle, is critical for estimating particle deposition rate and for simulation of particle transport using approaches such as the hard-sphere discrete element method (DEM). The problem is complicated by the fact that several different damping mechanisms act to inhibit particle rebound from the wall, even for the relatively simple case of normal particle impact. While comparisons of theoretical expressions for different damping mechanisms (e.g., viscoelastic damping, squeeze-film damping, plastic damping, van der Waals adhesion, etc.) are typically conducted with consideration of only one damping mechanism, in practice all of these mechanisms must be accounted for to make appropriate comparison of predictions with experimental data. The current paper presents a simplified model that integrates previous theoretical expressions for these different damping mechanisms. The integrated analytical expression yields predictions for particle normal restitution coefficient that are in excellent agreement with experimental data over a wide range of impact velocities. A sensitivity analysis was conducted using the method of variances to examine the influence of different parameters and different damping forces on measures of the restitution coefficient output.