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Understanding the role of surface morphology and molecular structure interface thermal transport is essential for designing thermal management materials. In the present work, models of solid–liquid interfaces were created by placing liquid n-alkane between two platinum crystals. The effect of different levels of crystal surface roughness–flat, small, and large-scale grooves–and polymer chain lengths, under varying solid–liquid affinity, on the interface thermal resistance (ITR) were assessed using non-equilibrium molecular dynamics simulations. The overall trend confirmed that grooved surfaces have higher ITR than flat surfaces at low affinity, and lower ITR values were observed at high affinity. Large grooves enabled more favourable polymer orientations than those of small grooves, resulting in a smaller ITR. However, long chains did not facilitate heat transfer normal to the interface because they preferentially aligned parallel to it. For efficient heat transfer, a balance between the roughness scale and polymer length must be considered. [ABSTRACT FROM AUTHOR]

Context: Ammonium perchlorate (NH4ClO4, abbreviated as AP) has the advantages of high oxygen content, high density, and good compatibility, and has significant application prospects in the field of energetic materials. The crystal morphology has a great influence on the properties and sensibility of energetic materials, and a single experimental means is difficult in exploring the crystals; therefore, the crystal morphology of AP is investigated using molecular dynamics simulation complemented with experiments, to theoretically analyze the differences in AP crystal habit and the interactions between solvent molecules and the main growing crystal surfaces of AP. The results show that AP crystal is mainly composed of five independent crystal surfaces (0 0 1), (0 1 0), (1 0 0), (1 0 1), and (1 0 −1) in vacuum using the BFDH laws, with (0 0 1) surface being the main growth crystal surface. In contrast, in H2O solvent, the (1 0 1) and (1 0 −1) surfaces disappear, and the AP mainly consists of (0 0 1), (0 1 0), and (1 0 0) surfaces with a rectangular shape. The crystal morphology obtained from theoretical prediction is in good agreement with that obtained from experimental culture. This paper can provide a new idea for the cultivation and preparation of AP large crystals, and promote the application of AP crystals in energetic materials. Methods: The crystal morphologies of AP in vacuum and H2O solvent under Dreiding force field were predicted based on attachment energy model by using molecular dynamics method in Materials Studio 2019 software. The entire molecular dynamics simulation was carried out under the NTV system, the temperature control method was selected as Anderson, and the system temperature was set to 298 K. The simulation time was set to 40 ps, the step size was set to 1 fs, and the data were outputted every 5000 steps. [ABSTRACT FROM AUTHOR]

Context: Ammonium perchlorate (NH4ClO4, abbreviated as AP) has the advantages of high oxygen content, high density, and good compatibility, and has significant application prospects in the field of energetic materials. The crystal morphology has a great influence on the properties and sensibility of energetic materials, and a single experimental means is difficult in exploring the crystals; therefore, the crystal morphology of AP is investigated using molecular dynamics simulation complemented with experiments, to theoretically analyze the differences in AP crystal habit and the interactions between solvent molecules and the main growing crystal surfaces of AP. The results show that AP crystal is mainly composed of five independent crystal surfaces (0 0 1), (0 1 0), (1 0 0), (1 0 1), and (1 0 −1) in vacuum using the BFDH laws, with (0 0 1) surface being the main growth crystal surface. In contrast, in H2O solvent, the (1 0 1) and (1 0 −1) surfaces disappear, and the AP mainly consists of (0 0 1), (0 1 0), and (1 0 0) surfaces with a rectangular shape. The crystal morphology obtained from theoretical prediction is in good agreement with that obtained from experimental culture. This paper can provide a new idea for the cultivation and preparation of AP large crystals, and promote the application of AP crystals in energetic materials. Methods: The crystal morphologies of AP in vacuum and H2O solvent under Dreiding force field were predicted based on attachment energy model by using molecular dynamics method in Materials Studio 2019 software. The entire molecular dynamics simulation was carried out under the NTV system, the temperature control method was selected as Anderson, and the system temperature was set to 298 K. The simulation time was set to 40 ps, the step size was set to 1 fs, and the data were outputted every 5000 steps. [ABSTRACT FROM AUTHOR]

The premelting layer on crystal surfaces significantly affects the stability, surface reactivity, and phase transition behaviors of crystals. Traditional methods for studying this layer—experimental techniques, classical simulations, and even first-principle simulations—have significant limitations in accuracy and scalability. To overcome these challenges, we employ molecular dynamic simulations based on neural network potentials to investigate the structural and dynamic behavior of the premelting layer on ice. This approach matches the accuracy of first-principle calculations while greatly improving computational efficiency, allowing us to simulate the ice–vapor interface on a much larger scale. In this study, we conducted a one-nanosecond simulation of the ice–vapor interface involving 1024 water molecules. This significantly exceeds the time and size scales of previous first-principle studies. Our simulation results indicate complete surface melting. Furthermore, our simulation results reveal dynamic heterogeneity within the premelting layer, with molecules segregated into clusters of low and high mobility. [ABSTRACT FROM AUTHOR]

Silicon carbide (SiC) plays a vital role in devices used in several fields, such as communications, displays, and lighting. The quality of SiC growth is critical to the fabrication of high-performance SiC devices; thus, it is important to explore its growth mechanism. Herein, we used approaches based on molecular dynamics to simulate the induced crystallization process of 3C-SiC crystal based on a solid–liquid model. In addition, we proposed an expression for the degree of nonuniform crystal growth, allowing us to dynamically and quantitatively describe the crystal growth process. The results show that the crystal growth quality is unsatisfactory at low temperatures, with a high defect density and uneven growth of crystal faces. In addition, the process of SiC crystal growth generates rival growth patterns across each crystal growth direction, with the crystal preferentially proliferating along the direction with relatively lower growth competition. Although the system exhibits dislocation and void defects, the number of these defects exhibits opposing trends during relaxation. In addition, as crystal faces grow progressively, the process involving the filling of concave surfaces with crystal atoms is gradually transferred to the amorphous gaps within the system. Finally, this study provides insights into the formation of SiC crystal. [ABSTRACT FROM AUTHOR]

Crystalline nanocellulose is widely used for example, in the paper-making and food industries, as support matrix material or reinforcement of polymer materials, but also in drug carrier and nanomedicine applications. Interestingly, aqueous solutions of cellulose are extremely sensitive to small amounts of added salt yet mere considerations of charge screening leave open questions regarding the mechanisms, especially for unmodified cellulose in aqueous solutions. Here, we map NaCl ion distributions and the effect of added NaCl salt on the hydration of I β cellulose nanocrystal (CNC) surfaces by atomistic detail molecular dynamics simulations with explicit water solvent. The simulations reveal the dependency of the hydration layers of the six surfaces of CNCs on the ions, as well as NaCl ion binding sites, and preferences in terms of binding free energy for the ions near CNC surfaces at different NaCl concentrations. We discuss the modelling results against our prior rheology characterization of cellulose solutions. Together, the results indicate that the high sensitivity of cellulose aqueous solutions to added salt rises from the ions near the surface changing locally the ordering and structure of the hydration layers of the CNC surfaces. The revealed mechanism of salt-induced viscosity changes in cellulose aqueous solutions allows advanced design of gelling CNC systems for various end uses and may also guide tuning cellulose interactions by different solvent environments. [ABSTRACT FROM AUTHOR]

In this work, the dynamic behavior of nano-bubbles near the surface of single crystal iron (Fe) was investigated using molecular dynamics simulations. The cavitation erosion behavior of single crystal Fe and the structural evolution of its eroded surface was examined at different bubble diameters. The results show that nano-bubble diameter is inversely correlated with impact pressure and diameter is positively correlated with nanojet energy. The volume, surface area, and depth of cavitation pits are nearly directly proportional to the bubble diameter with correlation linear fitting coefficients of R2 = 0.9837, R2 = 0.9922, and R2 = 0.9799, respectively. Additionally, cavitation erosion induces the structural evolution of iron atoms from bcc to fcc and hcp structures. The percentage of new phase transformed is related to the bubble diameter and the type of transformed structure, the percentage of fcc and hcp structures of Fe atoms exhibits an increasing trend with the increase in the bubble diameter, and the Fe atoms of fcc structures occur an obvious increase beyond a bubble diameter of 12 nm. [ABSTRACT FROM AUTHOR]

In this work, the modified attachment energy model was used to predict the crystal morphology of isosorbide mononitrate (ISMN) in the dichloromethane (CH2Cl2) solvent system and dichloromethane-n-hexane (CH2Cl2-C6H14) mixed solvent system. The solvent effect can significantly affect the crystal morphology, which can profoundly impact both the drug's physicochemical properties and the subsequent technological treatment process. In addition, the interactions between solvent molecules and crystal faces were investigated using molecular dynamics simulation, and radial distribution function (RDF) analysis was performed to determine the types of interactions. The structural parameter S was introduced to characterize the roughness of each crystal surface; the change in the CH2Cl2 diffusion coefficient before and after the addition of C6H14 was analyzed using mean square displacement (MSD). The calculation results of the modified attachment energy from the two solvent systems revealed that C6H14 could accelerate crystal growth, while the crystal morphology was not greatly affected, which is of some significance as a guide for the industrial crystallization process. [ABSTRACT FROM AUTHOR]

Copyright of Chinese Journal of Explosives & Propellants is the property of Chinese Journal of Explosives & Propellants Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The surface free energy of solids, γ, plays a crucial role in all physical and chemical processes involving material surfaces. For the first time, we obtained γ directly from molecular dynamics simulations using a crystal cleavage method. The approach was successfully realized in a Lennard-Jones system by inserting two movable external walls, each consisting of a single crystal layer, into a bulk crystal to create flat, defect-free surfaces. The cleavage technique designed allowed us to calculate the surface free energy according to its definition and avoid surface premelting. The temperature dependence of γ was determined for the (100) and (110) crystal planes along the whole sublimation line and its metastable extension, up to T = 1.02 · Tm, where Tm is the melting point. Good agreement with indirect values of γ(T) was found. The proposed computational cleavage method can be applied to other solids of interest, providing valuable insight into the understanding of chemical and physical surface processes, and demonstrates the successful import of the cleavage method, traditionally used in technical preparation and study of crystal surfaces, into a modern atomistic simulation. [ABSTRACT FROM AUTHOR]

A novel non‐phosphorus and non‐nitrogen scale inhibitor IA‐HEMA was synthesized in the presence of only C, H and O using itaconic acid (IA) and 2‐hydroxyethyl methacrylate (HEMA) as the raw materials and hydrogen peroxide‐ascorbic acid (H2O2‐ASA) as the initiating system. The synthesis conditions were optimized with the response surface method (RSM). The results indicated that the material ratio had the largest effect on the scale inhibition rate, followed by initiator dosage, polymerization temperature and polymerization time successively. As demonstrated by the static scale inhibition experiment, the scale inhibition rate was 97.27 % when the IA‐HEMA concentration was 100 mg/L. The mechanism was explored by molecular dynamics (MD). The results indicated that IA‐HEMA was able to overcome its own distortion and adsorb on the crystal surface, and the scale inhibition performance was related to its chelating and lattice‐distortion ability, which effectively inhibited the formation and precipitation of scale. All these findings suggest that IA‐HEMA is a quite promising environmentally friendly scale inhibitor in the salt system. [ABSTRACT FROM AUTHOR]

The molecular dynamics method is used to further reveal, from the molecular point of view, the mechanisms of salt inhibiting the hydration of Na-MMT. The interaction between water molecules, salt molecules, and montmorillonite are calculated by establishing the adsorption models. According to the simulation results, the adsorption conformation, interlayer concentration distribution, self-diffusion coefficient, ion hydration parameters, and other data are compared and analyzed. The simulation results show that the volume and basal spacing increase in a stepwise manner with the increase of water content, and water molecules have different hydration mechanisms. The addition of salt will enhance the hydration properties of compensating cations of montmorillonite and affect the mobility of particles. The addition of inorganic salts mainly reduces the adsorption tightness between water molecules and crystal surfaces, thereby reducing the thickness of water molecules layer, while the organic salts can better inhibit migration by controlling interlayer water molecules. The results of molecular dynamics simulations reveal the microscopic distribution of particles and the influence mechanism when the swelling properties of montmorillonite are modified by chemical reagents. [ABSTRACT FROM AUTHOR]

In this work, 3Mg(OH)2·MgCl2·8H2O (318MHCH) nanowires with ultra-high aspect ratios were first synthesized by a liquid method, and the effects of cetyltrimethylammonium bromide (CTAB) in highly concentrated salt solution were investigated. The structure and morphology of the synthesized 318MHCH nanowires were characterized. The as-prepared 318MHCH nanowires have a typical triclinic structure and relatively good crystallization properties. By introducing CTAB, the aspect ratio of 318MHCH nanowires will significantly increase from 500 to 4000. The high aspect ratio of 318MHCH nanowires is due to the increase in solution viscosity and the selective adsorption of CTAB molecules on the crystal surface. FTIR, Raman and XPS spectroscopy confirmed that the positively charged nitrogen-containing head of the CTAB molecule interacts with the surface of the 318MHCH crystal. Furthermore, since the (−1 0 1) plane has a lower electrostatic potential, the nitrogen-containing head of CTAB with a high potential is more readily adsorbed, which was confirmed by molecular dynamics simulations. Therefore, CTAB is selectively adsorbed on the side of 318MHCH nanowires, hindering the lateral growth and promoting the aspect ratio of 318MHCH nanowires. In addition, other cationic surfactants have been shown to have similar effects on the selective growth of nanowires. [ABSTRACT FROM AUTHOR]

How to effectively control the growth behavior of gypsum crystal in solution system has become one of the urgent problems to be solved in desulfurization industry, and the effective information of crystal growth process can' t be detected online timely and effectively. In this work, molecular dynamics simulation ( MS ) was used to calculate adhesion energy, face-center distance and area of specific plane of gypsum crystal, to determine morphologically dominant crystal planes and surface structure, and to theoretically study the interaction mechanism between sodium chloride and the main growth planes. The effect of sodium chloride on the crystal morphology of gypsum was obtained through experiments, which was compared with the results of MS. Results showed that sodium chlorides have varied effects on each crystal planes of gypsum crystals, which further changing the crystal morphology of gypsum. The simulation results are consistent with the experiment. MS can provide a theoretical support for morphology control of gypsum crystals. [ABSTRACT FROM AUTHOR]

To investigate the crystallization of DNTF in modified double-base propellants, glycidyl azide polymer (GAP) was used as the coating material for the in situ coating of DNTF, and the performance of the coating was investigated to inhibit the crystallization. The results show that GAP can form a white gel on the surface of DNTF crystals and has a good coating effect which can significantly reduce the impact sensitivity and friction sensitivity of DNTF. Molecular dynamics was used to construct a bilayer interface model of GAP and DNTF with different growth crystal surfaces, and Molecular dynamics calculations of the binding energy and mechanical properties of the composite system were carried out. The results showed that GAP could effectively improve the mechanical properties of DNTF. The values of K/G, γ and ν are higher than those of DNTF crystals, and the values of C12-C44 are positive, indicating that GAP can improve DNTF ductility while also improving toughness. Combining the experimental results with the simulation calculations, energetic binder GAP can be referred to as a better cladding layer for DNTF, which is feasible for inhibiting the DNTF crystallization problem in propellants. [ABSTRACT FROM AUTHOR]

Understanding crystallization mechanisms in nano-sized metallic glasses (MGs) is important to the manufacturing and application of these new nanomaterials that possess a unique combination of structural and functional properties. Due to the two-dimensional projections and limited spatial and/or temporal resolutions in experiments, significant questions (e.g., whether nucleation takes place on the free surface or in a near-surface layer) regarding this subject remain under debate. Here, we address these outstanding questions using molecular dynamics simulations of crystallization in MG nanorods together with atomistic visualization and data analysis. We show that nucleation in the nano-sized MGs predominantly takes place on the surface by converting the high-energy liquid surface to a lower-energy crystal surface (the most close-packed atomic plane). This is true for all the nanorods with different diameters studied. On the other hand, the apparent growth mode (inward/radial, lateral or longitudinal) and the resulting grain structure are more dependent on the nanorod diameter. For a relatively big diameter of the nanorod, the overall growth rate does not differ much among the three directions and the resulting grains are approximately semispherical. For small diameters, grains appear to grow more in longitudinal direction and some grains may form relatively long single-crystal segments along the length of the nanorod. The reasons for the difference are discussed. The study provides direct atomistic insights into the crystallization mechanisms in nano-sized MGs, which can facilitate the manufacturing and application of these new advanced materials. [ABSTRACT FROM AUTHOR]

We develop a ReaxFF reactive force field used for the molecular dynamics simulations of thermophysical properties of liquid Cu and Zr metals. The ReaxFF parameters are optimized by fitting to the first-principles density-functional calculations on the equations of state for bulk crystal structures and surface energies. To validate the force field, we compare the ReaxFF results with those from experiments and embedded-atom-method (EAM) potentials. We demonstrate that the present ReaxFF force field well represents structural characteristics and diffusion behaviors of elemental Cu and Zr up to high-temperature liquid regions. It reasonably reproduces the thermodynamic processes associated with crystal-liquid interface. In particular, the equilibrium melting temperatures show better agreement with experimental measurements than the results from EAM potentials. The ReaxFF reactive force field method exhibits a good transferability to the nonreactive processes of liquid systems. [ABSTRACT FROM AUTHOR]

Transition metal dichalcogenides (TMDs) have attracted significant interest as gas‐sensing materials due to their unique crystal structure and surface. However, there are still issues when it comes to expanding the types of sensing gases for the TMD gas sensors. To extend gas‐sensing selectivity for the TMD gas sensors in this study, a monolayer (ML) 2D metal–organic framework (MOF) is introduced on top of the PtSe2 gas sensor, thereby tuning the major sensing analyte of PtSe2 from NO2 to H2S. Density functional theory calculations elucidate that the metal species of ML MOFs are attributed to the tuned selectivity of the analytes, based on the difference in binding energies. It is also demonstrated that ML MOF maintained the high responsivity of the pristine PtSe2 even at a low concentration of gas (200 ppb). This is further confirmed through the molecular dynamics simulations, which reveal that the ML feature of the ML MOF is highly essential to preserve the intrinsic ultra‐low limit detection properties of pristine PtSe2. [ABSTRACT FROM AUTHOR]

Based on the modified embedded atom method (MEAM) potential suggested by Jin et al. (Appl. Phys. A120: 189, 2015), the molecular dynamics (MD) simulations were adopted to investigate the melting transition of the FCC transition metal Ni, and in the MD simulations, the forces acting on atoms were calculated by using the newly derived formulas. We first studied the melting points of Ni samples with low-index surfaces including Ni(100), Ni(110), and Ni(111). Then, we investigated the structural properties on the surface layers with increasing temperature up to the melting points. The simulation results exhibit that with the temperature increasing, the (110) surface firstly disorders, followed by the (100) surface, while the stability of the (111) surface is maintained until near the melting point. The disorder of surface layer atoms diffuses from the surface to the inside of the crystal lattice. With the density of atoms decreasing on the surface, the premelting effect also increases, being most pronounced on Ni(110) which corresponds to the lowest surface density. This conclusion is linked with the behavior found for the BCC transition metal Fe in our previous simulation study. [ABSTRACT FROM AUTHOR]

During the operation of the boiler, the ash deposition phenomenon in the furnace will cause abnormal operation of the boiler system. This will lead to an increase the pollutant emission. To relieve the pollutant emission during the abnormal operation of the boiler, the mechanism of ash deposition was investigated from the perspective of reducing the phenomenon for ash deposition in this paper. Calcium-containing compounds play an important role in ash deposition burning coal. Therefore, the influence of calcium-containing compounds on ash deposition was investigated with Zhundong coal in a horizontal tube furnace in this paper. Furthermore, the binding and diffusion properties of calcium-containing compounds on the oxide film's surface were characterized under different temperatures by molecular dynamics simulations. The growth process of surface crystals was also researched by kinetic Monte Carlo method. The results indicated the precipitation rate of calcium gradually increases with the increase of combustion temperature. CaO, CaSO4, and CaSiO3 can play an important role in ash deposition burning Zhundong coal. CaSO4 is more easily to react with α–Fe2O3 (110) than CaO or CaSiO3. The diffusion coefficient of CaSO4, CaO, or CaSiO3 increases gradually with the increase of temperature. Furthermore, the system composed of CaSO4 and oxide film is more affected by temperature than that of CaO or CaSiO3 and oxide film. Moreover, under the whole temperature, the content of CaSO4 on the surface of the oxide film is the most. Finally, three calcium-containing minerals can promote each other during the deposition process and accelerate the formation of ash deposits. [ABSTRACT FROM AUTHOR]

In ultra-precision machining, material anisotropy has an essential impact on surface generation and subsurface damage. In this work, the molecular dynamics method is applied to create the diamond nano-cutting models of Ni-based single crystal (NBSX) superalloy workpieces with different crystal orientations, and the surface/subsurface damage characteristics, crystal structure changes, cutting force, and atomic temperature and stress are discussed. The results show significant differences in surface/subsurface quality, crystal structure transformation, cutting force, atomic temperature and stress distributions and dislocation density obtained from nano-cutting workpieces along different crystal orientations. In four groups of workpieces, the surface/subsurface quality is used as an evaluation index, which shows that the [110](001) crystal orientation has the best cutting effect, and the [111](1 ‾ 10) crystal orientation is the worst cutting direction. This work reveals the damage generation mechanism of the machined surface/subsurface of NBSX superalloy on an atomic scale, which provides technical support for improving machining quality and optimizing machining parameters. [Display omitted] • Surface/subsurface damage characteristics are formed by different crystal orientations. • The workpiece with the [110](001) crystal orientation has the optimal surface/subsurface quality. • Material stress induces the formation of dislocations and defects, and three deformation zones appear in the tool-to-workpiece contact area. • The temperature drop point is closely related to chips and side flow. [ABSTRACT FROM AUTHOR]

• The crystal morphology of the CL-20/TFAZ cocrystal was predicted using modified attachment energy in solvent. • Crystal shape becomes closer to a stereoscopic shape in IPA/EA solvents. • The interaction between CL-20/TFAZ cocrystal and various solvents was analyzed using radial distribution function. • Mean square displacement method was used to analyze the diffusion coefficients of various solvents in CL-20/TFAZ cocrystal. Crystal morphology of CL-20/TFAZ cocrystal in vacuum was predicted using the attachment energy (AE) model. Additionally, the modified attachment energy (MAE) model and molecular dynamics (MD) method were utilized to predict the crystal morphology of CL-20/TFAZ cocrystal in four different binary solvents, namely, isopropyl alcohol (IPA)/acetone (AC), IPA/dimethyl sulfoxide (DMSO), IPA/ethyl acetate (EA), and IPA/water (H 2 O). The radial distribution function (RDF) between the solvent and crystal surface and the mean square displacement (MSD) of the solvent were calculated. The findings showed that the morphology of CL-20/TFAZ cocrystal in vacuum was an irregular polyhedron with eleven important growth surfaces: (0 0 1), (1 −1 0), (1 1 0), (1 0 0), (0 1 1), (0 −1 1), (1 0 −1), (0 2 0), (0 −2 0), (1 1 −1), and (1 −1 −1), with the (0 0 1) surface having the highest area ratio of 31.693 %. The crystalline morphology in IPA/AC, IPA/DMSO, and IPA/EA solvents was block-shaped, while it was rod-shaped in IPA/H 2 O. Comparing the RDF values of the four solvents, IPA/H 2 O exhibited the largest g(r) value and could more easily adsorb onto the crystal surface of CL-20/TFAZ cocrystal. Interestingly, IPA/H 2 O solvent had the smallest MSD value, suggesting the slowest diffusion rate, while IPA/AC solvent exhibited the fastest diffusion rate. Overall, IPA/EA solvents were more suitable for the formation of CL-20/TFAZ cocrystal. [ABSTRACT FROM AUTHOR]

Silicon carbide (SiC) crystal is a third-generation semiconductor material, which is widely used in the fields of radio frequency components, aerospace, new energy vehicles, etc. The anisotropy of 4H–SiC leads to differences in material removal characteristics of different crystal surfaces, which influences the design of process parameters for SiC crystal polishing. A model of single abrasive scratching 4H–SiC crystal was established using molecular dynamics. The effect of scratching speed and depth on the material removal characteristics and the wafer surface morphology was investigated when a single abrasive scratches the C surface and Si surface. Scratching experiments were conducted to verify the model by measuring scratch cross-sectional area, scratch profile, and surface roughness. The simulation results reveal that compared to the Si surface, the distribution range of high hydrostatic stress of the C surface is less, resulting in fewer amorphous atoms and easier dislocation, which means the C surface is more favorable for getting plastic removal and obtaining better surface quality. The experiment data suggested that the C surface has a smaller surface roughness and a friction coefficient, and the cross-sectional area of the scratch is larger than that of the Si surface. Under low-speed conditions, the influence of anisotropy is more pronounced. Consistent with the simulation result, the material removal characteristics of the C surface are better than those of the Si surface when single abrasive scratching 4H–SiC crystal. [ABSTRACT FROM AUTHOR]

Using shock‐induced quasi‐2D pore collapse in β‐HMX as a specific case study, we address three practical questions that arise when designing and interpreting molecular dynamics (MD) simulations of explicit shock wave propagation in crystals. How sensitive are the overall results to sample thickness perpendicular to the (quasi) plane of the problem? For impacts on a given crystal surface, how much does the transverse orientation of the sample matter? And, for a given sample size and orientation, how much run‐to‐run variability exists among results for independent but statistically equivalent realizations of the shock? The first and second questions are interrelated but pertain individually to assessing the roles of finite‐size and crystal anisotropy effects, respectively, on the simulated collapse mechanisms and associated local thermo‐mechanical states in the sample during and after collapse. The third addresses the confidence with which the results of individual simulations can be regarded as representative. All three questions become particularly important if the MD predictions are intended to serve as "ground truth" for validation of continuum mesoscale models. Here, quasi‐2D samples of (010)‐oriented single‐crystal β‐HMX (β‐1,3,5,7‐tetranitro‐1,3,5,7‐tetrazocane) containing a cylindrical pore were subjected to reverse‐ballistic impacts, resulting in explicit, supported shock propagation initially along [010], for impact speeds up =1.0 and 0.5 km s−1. The individual samples differed in either the thickness perpendicular to the sample plane or the transverse crystal orientation normal to [010] in the quasi‐2D cell. Three independent realizations of the shock were performed for a selected case to assess run‐to‐run variability. Comparisons of qualitative features of the collapse, temperature and pressure distributions in the samples, and time scales for pore collapse suggest that there is little sensitivity to sample thickness for the same crystal orientation and moderate sensitivity to transverse crystal orientation for samples of the same thickness. Run‐to‐run variability is evident to the eye in side‐by‐side system observations. However, overall mechanisms of collapse, distributions for temperature and pressure in the samples, and time scales for collapse are in near‐quantitative agreement among the realizations. [ABSTRACT FROM AUTHOR]

aligning surface for preorientation of low molecular weight liquid crystals in a bulk. The brush is built by grafting the polymer chains of a side-chain molecular architecture, with the side chains terminated by a chromophore unit mimicking the azobenzene unit, to a substrate. When irradiated with ultraviolet light, the chromophores photoisomerize into a non-mesogenic cis state and the whole system turns into an ordinary polymer brush with no orientationalorderandtwostates:thecollapsedandstraightenedone,dependingonthegraftingdensity.When irradiated with visible light, the chromophores photoisomerize into a mesogenic trans state, resulting in formationofatransientnetworkbetweenchainsbecauseofastrongattractionbetweenchromophores. Spontaneous self-assembly of the brush in these conditions results in an orientationally isotropic polydomain structure. The desired uniaxial planar ordering of chromophores within a brush can be achieved at certain temperature and grafting density intervals, as the result of a two-stage preparation protocol. An external stimulus orients chromophoresuniaxiallyatthefirststage. Thesystemisequilibratedatthesecondstageatagiventemperatureand with the external stimulus switched off. The preoriented chromophores either keep or loose their orientations depending on the strength of the memory effect inherent to a transient network of chains that are formed during the first stage, similarly to the case of the liquid crystalline elastomers, where such effects are caused by the covalent crosslinks. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Guangdong University of Technology is the property of Journal of Guangdong University of Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Dendrite formation occurs on Li, Na, and Mg metal anodes in rechargeable batteries, and is a safety challenge, as well as a limiting factor for increasing energy- and power density. However, the behaviour of the dendrites differs depending on the anode material. In this study, we investigate the local bulk and surface crystal structure of Li, Na, and Mg surfaces to shed light on how differences in the morphology and structure of the anode surface and its metal deposits can explain differences in dendrite formation on Li, Na, and Mg anodes. The local bulk- and surface structure are found using molecular dynamics simulations in combination with the surface adaptive common neighbour analysis, and indicate that Li and Na surfaces are more prone to surface instabilities and formation of protrusions than Mg surfaces, which remain flat and hexagonal close-packed even near room temperature. Additionally, the equilibrium shapes of the Mg deposits obtained from density functional theory assume more flat and hexagonal shapes than the Li and Na deposits. Together, these results shed light on atomic mechanisms that may contribute to the different propensities of Li, Na, and Mg metal anodes to form dendrites. [ABSTRACT FROM AUTHOR]

The manuscript presents a trajectory method for describing the rotations of surface crystals such as fullerenes, nanotubes, and nanotori. This method does not require the implementation of successive rotations of the considered molecular structures around the axes of the selected basis. Therefore, it is free from the shortcomings of the approaches of Euler and Hamilton. On its basis, an efficient algorithm for calculating the motions of a magneto-susceptible fullerene in an alternating magnetic field has been developed. The nature of rotation of fullerenes in fields of various configurations has been studied. [ABSTRACT FROM AUTHOR]

Plasma anisotropic etching polishing (plasma-AEP), a non-contact polishing method, is proposed to achieve highly efficient planarization of polycrystalline diamond (PCD) films. Inductively coupled plasma, with a high concentration of reactive radicals, serves as the source of plasma-AEP. In-situ observation confirms that the planarization effect of plasma-AEP is realized through the preferential removal of the top areas of the pyramid-shaped protrusions, despite the entire surface being uniformly irradiated by the plasma. The material removal rate in plasma-AEP for PCD achieves 127 μm/min. Plasma-AEP is proven effective for PCD films with thicknesses of 0.5, 1, and 2 mm, demonstrating a generic semi-finishing approach for PCD regardless of thickness. Atomic-scale nudged elastic band calculations revealed that the energy barriers for CO and CO 2 desorption from 1- and 2-coordinated C atoms are significantly lower than those for 3- and 4-coordinated ones. ReaxFF molecular dynamics simulations showed that at the top areas of the pyramid-shaped protrusions, 1- and 2-coordinated C atoms with a higher etching priority remained dominant during plasma-AEP, leading to the preferential removal of C atoms forming these protrusions. Furthermore, contact polishing was added to complete the finishing of the PCD film, followed by plasma-AEP, resulting in a nanoscale smooth surface with a roughness of 3.4 nm. Transmission electron microscopy confirmed that the crystal structures on the surface and subsurface of the PCD film were well ordered. Overall, this paper displays that plasma-AEP is a promising approach for highly efficient semi-finishing of PCD films. [Display omitted] • Plasma anisotropic etching polishing (plasma-AEP) is developed. • Preferential removal of protrusions on polycrystalline diamond (PCD) is confirmed. • The anisotropic etching characteristic is revealed by multi-scale simulations. • Plasma-PAE is generic for semi-finishing PCD with various thicknesses. • Contact polishing is added to achieve nanoscale finishing of PCD. [ABSTRACT FROM AUTHOR]

Currently, laser-induced damage is a prominent focus in the field of ultrafast laser micro/nano processing. This article focused on the potential formation thickness of the ultrafast laser-induced sapphire crystal surface recast layer. To investigate the influence of laser parameters and crystal orientation on the recast layer potential formation thickness at the atomic scale, a molecular dynamics model of laser irradiation sapphire crystal was constructed. Experiments of laser-induced recast layer formation were carried out, and the effects of laser fluence, pulse width, and wavelength on the surface recast layer were analyzed. The results show that the ejected atom start formation time is significantly influenced by pulse width, while the potential formation thickness of the recast layer is mainly influenced by the deposited laser energy. Moreover, under the same laser energy, the damage extent in sapphire crystal caused by laser irradiation along the (0001) orientation is significantly weaker compared to irradiation along the (1–100) and (11–20) orientations. This article could provide theoretical and process references for suppressing the ultrafast laser-induced sapphire crystal surface recast layer formation. [ABSTRACT FROM AUTHOR]

This work carried out research of the adsorption processes of O2 molecules on ZnO nanoclusters under different initial conditions by molecular dynamics method. To describe the interaction between atoms, we used the reactive force field (ReaxFF) interatomic potential. Several computer experiments were conducted with different initial conditions. We have been found that the whole process of adsorption was divided into two stages, the first stage was characterized by a rapid increase in the number of adsorbed molecules, the second one an increase of fluctuations in the change of adsorbed molecules on the surface over time. The higher gas pressure in the system corresponds to the greater number of O2 molecules diffusing into the volume of the ZnO nanocluster, therefore, the crystal structure of the surface of the ZnO nanocluster becomes amorphous. In addition, it was established that the tendencies of distribution of the dependence of the central symmetry parameter with the oxygen concentration in the system (NO2 < 100 molecules) were similar. The situation was quite different when the number of oxygen molecules increased: the value of the central symmetry parameter of surface atoms was more evenly distributed, which cannot be considered as a crystalline state of ZnO nanocluster. [ABSTRACT FROM AUTHOR]

Arginine‐modified polyepoxysuccinic acid (Arg‐PESA) was used as a scale inhibitor to study its anti‐scaling and anti‐corrosion performance. The existence of arginine groups enhances the adsorption and chelation of calcium substances, thus inhibiting the formation of a calcium scale. The effects of temperature, scale inhibitor concentration, pH, and calcium ion concentration on scale inhibition performance were studied. The morphologies and structures of the calcium scale and carbon steel coupons were observed and characterized by spectroscopic and microscopic methods. The interaction between Arg‐PESA and different crystal surfaces of calcium carbonate was simulated by molecular dynamics to elucidate the anti‐scaling mechanism. The addition of Arg‐PESA also significantly enhanced the dispersion of iron oxide. [ABSTRACT FROM AUTHOR]

Solvents can dramatically affect molecular crystals. Obtaining favorable properties for these crystals requires rational design based on molecular level understanding of the solid–solution interface. Here we show how atomic force microscopy combined with molecular dynamics simulations can be utilized for understanding critical surface properties, namely crystallinity and hydrophobicity, as crystals are exposed to water–ethanol mixtures. We report the formation of dynamic heterogeneous disordered surface (DHDS) layers at the solid–solution interface. The observed DHDS layer was affected by the solvent composition and a variation in the water–ethanol ratio caused significant changes in surface properties. [ABSTRACT FROM AUTHOR]

The release of clusters from the surface of PuO 2 nanocrystals caused by the alpha decay collision cascades was simulated using the molecular dynamics. The clusters containing up to several hundred particles were recorded. The obtained size distributions of the clusters were characterized by relatively high probabilities of the formation of large clusters. The total kinetic energy of the released material reached tens of percent of the total energy of the collision cascade. Single ions, both plutonium and oxygen, could have kinetic energies of up to several thousand electron-volts. The electric charge of the clusters in most cases was close to zero, although clusters with significant negative charges were also observed. [ABSTRACT FROM AUTHOR]

The advanced spiral growth model that considers the thermodynamics and kinetics aspects of the adsorption process is applied to predict the growth habits of the nitroguanidine crystal in water and γ-butyrolactone. The molecular dynamics simulations were performed to search for the equilibrium state of the interface model. The predicted results show that the crystal shapes of nitroguanidine in water and γ-butyrolactone are needlelike and flake-like shape, respectively, which agrees remarkably well with the experiment. In water, the (011) face constitutes an overwhelming 96.17% of the total crystal surface area, and the crystal grows rapidly along the [111] direction. In γ-butyrolactone, the (011) face is exposed, but its area only accounts for 15.56%. The (011) face and the mostly exposed (001) face form a surrounding surface in a flake-like shape. Furthermore, periodic bond chains are used to analyze the growth process of different crystal faces. [ABSTRACT FROM AUTHOR]

Binding of biomolecules to crystal surfaces is critical for effective biological applications of crystalline nanomaterials. Here, we present the modulation of exposed crystal facets as a feasible approach to enhance specific nanocrystal–biomolecule associations for improving cellular targeting and nanomaterial uptake. We demonstrate that facet-engineering significantly enhances transferrin binding to cadmium chalcogenide nanocrystals and their subsequent delivery into cancer cells, mediated by transferrin receptors, in a complex biological matrix. Competitive adsorption experiments coupled with theoretical calculations reveal that the (100) facet of cadmoselite and (002) facet of greenockite preferentially bind with transferrin via inner-sphere thiol complexation. Molecular dynamics simulation infers that facet-dependent transferrin binding is also induced by the differential affinity of crystal facets to water molecules in the first solvation shell, which affects access to exposed facets. Overall, this research underlines the promise of facet engineering to improve the efficacy of crystalline nanomaterials in biological applications. Modulation of exposed crystal facets enhances transferrin binding to chalcogenide nanocrystals and their subsequent delivery into cancer cells. Facet-dependent protein binding occurs through inner-sphere thiol complexation and is affected by the structure of the first solvation shell. [ABSTRACT FROM AUTHOR]

Solution crystallization is a common technique to grow advanced, functional crystalline materials. Supersaturation, temperature, and solvent composition are known to influence the growth rates and thereby properties of crystalline materials; however, a satisfactory explanation of how these factors affect the activation barrier for growth rates has not been developed. We report here that these effects can be attributed to a previously unrecognized consequence of solvent fluctuations in the solvation shell of solute molecules attaching to the crystal surface. With increasing supersaturation, the average hydration number of the glutamic acid molecule decreases and can reach an asymptotic limit corresponding to the number of adsorption sites on the molecule. The hydration number of the glutamic acid molecule also fluctuates due to the rapid exchange of solvent in the solvation shell and local variation in the supersaturation. These rapid fluctuations allow quasi-equilibrium between fully solvated and partially desolvated states of molecules, which can be used to construct a double-well potential and thereby to identify the transition state and the required activation barrier. The partially desolvated molecules are not stable and can attach spontaneously to the crystal surface. The activation barrier versus hydration number follows the Evans-Polanyi relation. The predicted absolute growth rates of the a-glutamic acid crystal at lower supersaturations are in reasonable agreement with the experimental observations. [ABSTRACT FROM AUTHOR]

• For the first time mass transfer by 2-crowdion is studied for realistic 3D crystal. • Impacts by Pt atom and Pt2 molecule on (1 0 1) surface of Pt crystal are compared. • Many-body EAM potential is used in molecular dynamics simulations. • Properly oriented molecule needs much smaller energy to initiate mass transfer. • Molecule impact can initiate propagation of supersonic 2-crowdion in platinum. Crystal surface bombardment by atoms or molecules, neutral or ionized, occurs both in ambient conditions and in many technological operations, such as surface plasma treatment, ion implantation, etc. Recently, it was established that the impact of a molecule initiates the mass transfer in the one-dimensional Frenkel-Kontorova atomic chain more efficiently than that of a single atom. This is explained by the fact that the atom can initiate only a very sharp, fast-moving crowdion (anti-kink), which requires relatively high energy, while the molecule is able to initiate a less localized crowdion with considerably lower velocity and energy. In the current study, by means of molecular dynamics simulation, for the first time, this phenomenon is studied for a realistic 3D model of platinum crystal. We compare the efficiency of single Pt atom impact and Pt 2 molecule impact on the (1 0 1) surface of fcc Pt crystal for the initiation of mass transfer in the material by crowdions. It is revealed that in order to generate a crowdion moving inside the crystal, the properly oriented molecule needs an order of magnitude smaller energy than single atom. This considerable reduction of required energy happens when the molecule is oriented perpendicularly to the crystal surface and hits the crystal along a close-packed atomic row. Furthermore, it is revealed for the first time that the molecule with sufficiently large velocity can initiate the so-called supersonic 2-crowdion, which travels longer distances in the crystal than the classical supersonic crowdion having same or even higher energy. Our results can be useful for understanding and prediction the mass transfer during technological applications where bombardment by atomic clusters is employed to modify and improve mechanical or functional properties of surfaces. [ABSTRACT FROM AUTHOR]

TOC Graphic Interfacial water and protein orientation modify the load-deformation response, conformations and the non-bonded interactions between protein with the mineral surface. Enamel is a composite bioceramic that covers teeth. Here, based on molecular dynamic (MD) simulation, we seek a better understanding of the interactions between the enamel matrix proteins with hydroxyapatite (HAP) crystal surfaces. These interactions occur during enamel formation and are responsible for controlling the formation of high aspect ratio carbonated hydroxyapatite nanocrystallites, whereas, in mature enamel, they are implicated to alter the mechanical properties of mature enamel to yield a tough composite that resists fracture during chewing. We choose an archetypal matrix protein known as tyrosine-rich amelogenin peptide (TRAP), which is retained among the HAP crystallites of mature enamel. Our findings provide molecular details to the emerging blueprint needed to engineer a biologically inspired enamel restorative material. [ABSTRACT FROM AUTHOR]

Quantitative structure-properties relationship (QSPR) method was used to design some novel antioxidant lubricant additives, while molecular dynamics simulations were used to calculate their dynamic binding energies on steel and to hydrogen-containing DLC (a-C: H) crystal surfaces. 29 synthesized antioxidant lubricant additives were collected from literature and geometrically optimized by Spartan'14 version 1.1.2 software while Genetic Function Algorithm (GFA) method of the material studio version 8.0 software was used to build the predictive QSPR model. Four novel antioxidant lubricant additives were successfully designed out of which E)-3-(4-((3-amino-4-methylphenyl)diazenyl)-5-hydroxy-4H-pyrazol-3-yl)-2-argio-6,7-difluoroquinazolin-4(3H)-one with excellent property of 3.531295 (KOH/g) was found to be better than the one reported by other researchers. The dynamic binding energy results revealed that one of the designed additives was excellently bound to steel (−1120.11 kcal/mol) and to hydrogen-containing DLC (a-C: H) crystals surface (7814.156 kcal/mol) surfaces than its co-additives. This investigation shows that the entire studied antioxidant lubricant additive was found to be better bound to the steel surface than hydrogen-containing DLC (a-C: H) crystals surface. This study will help in synthesizing novel anti-oxidant lubricant additives with better additive properties that will slow the tendency of oil to oxidize and will not possess a threat to the environment as the structures do not contain zinc and phosphorus that could limit the operation of the catalytic converter in the exhaust pipe. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • The role of interfacial fluctuations can be quantified using cumulant expansions. • Fluctuations near solid-liquid interface depend on the type of crystal surface. • The dampening of fluctuations depend on the type of crystal surface. • The actual contribution of interfacial fluctuations is small, but non-negligible. Abstract Transverse correlations (TCs) denote the correlations between density-fluctuations along the plane parallel to a solid-liquid interface. We use molecular simulations to investigate the TCs in a model fluid near static 100, 110 and 111 faces of BCC, FCC, and SC crystals of model solids. We use the cumulant expansions of solid-liquid interfacial free energies to quantify the contribution of TCs to the interfacial free energy. We approximately decompose the above contributions into those from TCs of different ranges. Our results show that the solid-fluid attractive interaction strongly dampens the TCs, and the extent of dampening depends on the exposed face of the crystal. We also observe that the contribution from TCs near the selected surfaces differ significantly even in absence of solid-fluid attractive interaction. Overall, our results indicate a great potential for tuning the solid-liquid interfacial fluctuations by altering the crystalline nature of solid surface. [ABSTRACT FROM AUTHOR]

Highlights • Pt3Al intermetallic alloy supports near-surface discrete breathers (DB). • Properies of DB depend on surface orientation and termination. • DB can localize energy about 1 eV. • DB can help to overcome potential barriers for structure transformations. Abstract It is known that defect-free crystals can support spatially localized, large amplitude vibrational modes with frequencies outside the linear phonon spectrum. Such excitations are called discrete breathers (DB) or intrinsic localized modes. So far, for 3D crystals DB were considered only in the bulk. In the present molecular dynamics study, for the first time, we demonstrate that DB can be excited at the low Miller indices surfaces of the Pt 3 Al intermetallic alloy. It is shown that properties of the DB depend essentially on the surface orientation and termination, as well as on DB polarization. The study of DB at crystal surfaces is important because they can localize energy of order of 1 eV, which can reduce the potential barrier for local structure transformation or a chemical reaction. Graphical abstract Image, graphical abstract [ABSTRACT FROM AUTHOR]

The adsorption of water and ions on ettringite crystal, an important hydration product in the cement material, is fundamental to the durability of cement-based material. In this study, molecular dynamics was utilized to investigate the molecular structure, dynamics and interfacial bonding for the water and ions in the vicinity of ettringite crystal surface. The aluminate octahedron and sulfate ions in the surface of ettringite provide plenty of oxygen sites to accept H-bond from the water molecules in the interfacial region. The highly solvated surface calcium ions can strongly attract the neighboring water as their coordinate atoms. The hydrophilic nature of the ettringite interface results in the dramatically different feature of the water molecules on the ettringite surface, such as high dipole moment, ordered organization, good orientation preference and slow diffusivity. Furthermore, with gradually increasing simulation time, the calcium ions, aluminate and sulfate species in the crystal surface diffuse into the solution, resulting in the dissolution of the ettringite crystal and disturbance of the ordered interfacial topology. The six-coordinated aluminum hydroxyl groups transform to the aluminate tetrahedron, as they dissolve in the solution. Additionally, the chloride and sodium ions have different adsorption mechanism on the crystal surface. While the sodium ions are associated with the oxygen atoms in aluminate octahedron and sulfate ions by Na O ionic bond and immigrate into the inner region of the dissolved crystal, the chloride ions can form the ionic pairs with the calcium ions, accumulating to cluster in the outer layer region. As compared with the chloride adsorption, the ettringite crystal has better immobilization ability on the cation ions due to the stable Na O connection with long resident time. [ABSTRACT FROM AUTHOR]

We introduce Interfacial Line Defect Analysis (ILDA), a method for identifying and extracting interfacial dislocations and disconnections with little-to-no input from the user on the nature of the interface. By simply providing the orientations and coherency strains for the crystals in a coherent reference state of the interface, ILDA provides exact Burgers vectors. Alternatively, these orientations and strains can be estimated using local atomic deformation gradients, making ILDA fully automated and providing estimated Burgers vectors. ILDA also determines the step height associated with each defect line segment, in case the associated defect is a disconnection. The heart of the method is the identification of atoms residing at co-incidence sites between the two crystals and the construction of a surface mesh connecting these sites that is used to compose Burgers circuits and insert defect line segments. We demonstrate the performance of ILDA in two test cases: a twist grain boundary and a phase boundary. [Display omitted] [ABSTRACT FROM AUTHOR]

[Display omitted] • With the decrease of temperature, the order degree of the system is strengthened and the fluidity is weakened. • The diffusion coefficient of the H 2 O molecule is greater than that of the n C 5 H 12 molecule by a factor of ∼2. • At the same temperature, the diffusion coefficient of the n C 24 H 50 molecule in n C 5 H 12 is greater than that in H 2 O. • At temperatures of 50–20 °C, n C 24 H 50 molecules precipitate from the oil and gather on the pipe wall surface. Wax deposition on the inner wall of oil pipes, sucker rods, oil- and gas-gathering pipelines and equipment caused by wax crystals has been a challenging problem in the petroleum industry. At present, most of the marine terrestrial transitional facies and continental shale oil and gas being explored and developed in China have high-wax-content volatile oil or condensate, and many shale oil and gas wells have been seriously blocked by wax deposition. In this work, the wax deposition behavior of the binary alkane mixture n C 5 H 12 – n C 24 H 50 at different temperatures under the condition of water wetting of a pipe wall was studied through molecular dynamics simulation. When the temperature is 130–70 °C, the wax molecules are loosely distributed without obvious aggregation, and the pipe wall is mainly occupied by water molecules, exhibiting a water-wetting state. With the decrease in temperature, the distance between n C 24 H 50 molecules decreases correspondingly, which enhances the interaction between wax molecules and increases the probability of mutual aggregation. When the temperature is 50 °C, a small amount of n C 24 H 50 molecules pass through the water molecular layer and gather on the pipe wall. When the temperature is <50 °C, the binding energy between the crystal surface of the pipe wall and the molecule n C 24 H 50 exhibits a first-order phase transition, and the molecule n C 24 H 50 can more easily bind to the pipe wall than the molecule H 2 O. When the temperature is 40–20 °C, the aggregation amount of n C 24 H 50 molecules on the pipe wall further increases, exhibiting an obvious crystallization tendency, and a small amount of n C 5 H 12 molecules begin to aggregate with n C 24 H 50 molecules through the water molecular layer on the pipe wall. At the same temperature, the diffusion speed of n C 24 H 50 molecules in n C 5 H 12 is faster than that in H 2 O. [ABSTRACT FROM AUTHOR]

Bombyx mori Silk Fibroin-hydroxyapatite (B. mori SF-HA) bio-nanocomposite is a prospective biomaterial for tissue engineered graft for bone repair. Here, B. mori SF is primarily a soft and tough organic phase, and HA is a hard and stiff mineral phase. In biomaterial design, an understanding about the nanoscale mechanics of SF-HA interface, such as interfacial interaction and interface debonding mechanisms between the two phases is essential for obtaining required functionality. To investigate such nanoscale behavior, molecular dynamics method is a preferred approach. Present study focuses on understanding of the interface debonding mechanisms at SF-HA interface in B. mori SF-HA bio-nanocomposite at nanometer length scale. For this purpose, nanoscale atomistic models of SF-HA interface are also developed based on the HA crystal size and HA surface type (Ca2+ dominated and OH− dominated) in contact with SF. Mechanical behavior analysis of these SF-HA interface models under pull-out type test were performed using Molecular Dynamics (MD) simulations. Surface pull-off strength values in the range of 0.4–0.8 GPa were obtained for SF-HA interface models, for different HA crystal thicknesses, wherein, the pull-off strength values are found to increase with increase in HA thicknesses. Analyses show that deformation mechanisms in SF-HA interface deformation, is a combination of shear deformation in SF phase followed by disintegration of SF phase from HA block. Furthermore, higher rupture force values were obtained for SF-HA interface with Ca2+ dominated HA surface in contact with SF phase, indicating that SF protein has a higher affinity for Ca2+ dominated surface of HA phase. Current work contributes in developing an understanding of mechanistic interactions between organic and inorganic phases in B. mori SF-HA composite nanostructure. [Display omitted] • Interface deformation mechanism include shear deformation in SF and debonding of SF from HA. • SF protein has higher affinity for Ca2+ dominated surface of HA phase. • Pull-off strength at SF-HA interface increase with increase in thickness of HA block. • H-bonds in SF and interface electrostatic contacts increase with increase in thickness of HA. • β-Sheet content decreases and random coils increase during interface deformation. [ABSTRACT FROM AUTHOR]

The 2,4,6,8,10,12-hexanitro-2,4,6,8,10,12-hexaazaisowurtzitane (CL-20)-solvent (methanol, ethanol, ethyl acetate and acetone) interfacial models were constructed to investigate the intermolecular interaction variances on different roughness surfaces. The constant volume and temperature molecular dynamics (NVT-MD) simulation was performed on the interfacial models. The mass density distributions of four kinds of solvent at interfaces were calculated based on the NVT-MD results. The surface electrostatic potential (ESP) of seven important extended CL-20 surfaces were studied at the B3LYP-D level with 6-311G (D) basis set. The interaction energies ( E int ), polarities of surfaces, radial distribution function (RDF) and number of H⋯O atom pairs were analyzed. The results show the largest densities of ethanol and acetone appear at the roughest (1 1 0) surface, while generating on the smoothest (1 1 −1) and (0 0 2) surfaces for methanol and ethyl acetate. ESP at the “basin” of (1 1 0) and (1 0 1) rough surfaces are negative, benefiting for attractions of solvent positive groups. RDF analysis indicates that the rough surfaces may be more beneficial for stronger non-bond interaction formation at the solvent-CL-20 interfaces. Results of interaction energies show that E int of the roughest surface [(1 1 0) or (1 0 1)] are the largest (most negative) and relative small at the smooth (0 0 2) surface, indicating the influence of solvent on rougher face growth is more significant. [ABSTRACT FROM AUTHOR]

We studied analytically and numerically the growth rate of a crystal surface growing by several screw dislocations. We observed some discrepancy between the growth rates computed by our level set method (J. Sci. Comput. 2015, 62, 831-874) and those reported by the classical paper of Burton et al. (Philos. Trans. R. Soc. London A 1951, 243, 299-358). To resolve the discrepancy, we propose a few improved estimates on the growth rate in several configurations. In particular, we give a quantitative definition of the critical distance of corotating screw dislocations under which the effective growth resembles that of a single spiral. We further study the growth rate of a crystal surface containing a group of screw dislocations. The proposed new estimates are in agreement with numerical simulations using the algorithm published by the authors (J. Sci. Comput. 2015, 62, 831-874). [ABSTRACT FROM AUTHOR]