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The permeability–selectivity trade‐off of membrane is a major challenge limiting the development of pervaporation (PV) technology. Rational design of high‐performance mixed matrix membranes (MMMs) has the potential to break off the trade‐off. Herein, a solvent‐assisted linker exchange‐based strategy is reported to introduce fluoroalkyl into metal–organic framework‐808 (MOF‐808). The pore size of fluorinated MOF‐808 can be adjusted with fluoroalkyl of different chain length (like trifluoromethyl and pentafluoropropyl). Then, the fluorinated MOF‐808/polyether block amide (PEBA) MMMs are prepared for the PV of n‐butanol/water. Compared with pristine PEBA membrane, 20 wt% 3F‐MOF‐808(P)/PEBA MMMs (3F = ‐CF3 group; P = postmodification method) exhibit 69% increase in permeation flux and 33% increase in separation factor in the PV of 2.5 wt% n‐butanol aqueous solutions at 70 °C. Based on Grand Canonical Monte Carlo and molecular dynamics simulations, fluorinated MOF‐808 shows better butanol affinity (pull effect) and stronger water repulsion ability (push effect). And the "push–pull effect" between fluorinated MOF‐808 with butanol/water is helpful to enhance the PV performance of MMMs. The application of "push–pull effect" provides a new strategy for the rational design of high‐performance MMMs, which is of great significance for the in‐depth research and application of PV technology. [ABSTRACT FROM AUTHOR]

The influenza BM2 transmembrane domain (BM2TM), an acid-activated proton channel, is an attractive antiviral target due to its essential roles during influenza virus replication, whereas no effective inhibitors have been reported for BM2. In this study, we draw inspiration from the properties of cyclodextrins (CDs) and hypothesize that CDs of appropriate sizes may possess the potential to act as inhibitors of the B M 2 T M proton channel. To explore this possibility, molecular dynamics simulations were employed to assess their inhibitory capabilities. Our findings reveal that CD4, CD5, and CD6 are capable of binding to the B M 2 T M proton channel, resulting in disrupted water networks and reduced hydrogen bond occupancy between H19 and the solvent within the B M 2 T M channel necessary for proton conduction. Notably, CD4 completely obstructs the B M 2 T M water channel. Based on these observations, we propose that CD4, CD5, and CD6 individually contribute to diminishing the proton transfer efficiency of the BM2 protein, and CD4 demonstrates promising potential as an inhibitor for the BM2 proton channel. [ABSTRACT FROM AUTHOR]

Inhibition of the Embryonic Ectoderm Development (EED) subunit in Polycomb Repressive Complex 2 (PRC2) can inhibit tumor growth. In this paper, we selected six experimentally designed EED competitive Inhibitors of the triazolopyrimidine derivatives class. We investigated the difference in the binding mode of the natural substrate to the Inhibitors and the effects of differences in the parent nuclei, heads, and tails of the Inhibitors on the inhibitory capacity. The results showed that the binding free energy of this class of Inhibitors was close to or lower compared to the natural substrate, providing an energetic basis for competitive inhibition. For the Inhibitors, the presence of a strong negatively charged group at the 6-position of the parent nucleus or the 8′-position of the head would make the hydrogen atom on the head imino group prone to flip, resulting in the vertical movement of the parent nucleus, which significantly decreased the inhibitory ability. When the 6-position of the parent nucleus was a nonpolar group, the parent nucleus would move horizontally, slightly decreasing the inhibitory ability. When the 8′-position of the head was methylene, it formed an intramolecular hydrophobic interaction with the benzene ring on the tail, resulting in a significant increase in inhibition ability. [ABSTRACT FROM AUTHOR]

Mechanical responses of nanoporous Cu samples under various loading conditions are investigated by molecular dynamics simulations. Effects of loading mode, initial void size, temperature, and void distribution are analyzed. The simulations show that the collapse time under uniaxial compression is about three times that under triaxial compression, and the collapse rate increases as the temperature rises. Dislocation nucleation is found to stimulate the collapse of void. For samples with a single void, the final dislocation density under triaxial compression is lower than that under uniaxial compression, which is due to that the dislocation accumulation rate greatly slows down after the void is fully collapsed. For samples with multiple voids, the dislocation accumulation rate under triaxial compression is much faster than that under uniaxial compression, resulting in higher dislocation density under triaxial compression. Irrespective of the initial void size, the evolutions of compression stress and void volume fraction remain invariant when the initial void volume fraction is fixed; however, the dislocation density decreases as the initial void radius increases. [ABSTRACT FROM AUTHOR]

E. coli thioesterase 'TesA is an important enzyme in fatty acid production. Medium-chain fatty acids (MCFAs, C6-C10) are of great interest due to their similar physicochemical properties to petroleum-based oleo-chemicals. It has been shown that wild-type 'TesA had better selectivity for long-chain acyl substrates (≥C16), while the two mutants 'TesAE142D/Y145G and 'TesAM141L/E142D/Y145G had better selectivity for medium-chain acyl substrates. However, it is difficult to obtain the selectivity mechanism of substrates for proteins by traditional experimental methods. In this study, in order to obtain more MCFAs, we analyzed the binding mode of proteins ('TesA, 'TesAE142D/Y145G and 'TesAM141L/E142D/Y145G) and substrates (C16/C8-N-acetylcysteamine analogs, C16/C8-SNAC), the key residues and catalytic mechanisms through molecular docking, molecular dynamics simulations and the molecular mechanics Poisson–Boltzmann surface area (MM/PBSA). The results showed that several main residues related to catalysis, including Ser10, Asn73 and His157, had a strong hydrogen bond interaction with the substrates. The mutant region (Met141-Tyr146) and loop107–113 were mainly dominated by Van der Waals contributions to the substrates. For C16-SNAC, except for 'TesAM141L/E142D/Y145G with large conformational changes, there were strong interactions at both head and tail ends that distorted the substrate into a more favorable high-energy conformation for the catalytic reaction. For C8-SNAC, the head and tail found it difficult to bind to the enzyme at the same time due to insufficient chain length, which made the substrate binding sites more variable, so 'TesAM141L/E142D/Y145G with better binding sites had the strongest activity, and 'TesA had the weakest activity, conversely. In short, the matching substrate chain and binding pocket length are the key factors affecting selectivity. This will be helpful for the further improvement of thioesterases. [ABSTRACT FROM AUTHOR]

Adhesion G-protein-coupled receptors (aGPCRs)—a major family of GPCRs—play critical roles in the regulation of tissue development and cancer progression. The orphan receptor GPR97, activated by glucocorticoid stress hormones, is a prototypical aGPCR. Although it has been established that the palmitoylation of the C-terminal Go protein is essential for Go's efficient engagement with the active GPR97, the detailed allosteric mechanism remains to be clarified. Hence, we performed extensive large-scale molecular dynamics (MD) simulations of the GPR97−Go complex in the presence or absence of Go palmitoylation. The conformational landscapes analyzed by Markov state models revealed that the overall conformation of GPR97 is preferred to be fully active when interacting with palmitoylated Go protein. Structural and energetic analyses indicated that the palmitoylation of Go can allosterically stabilize the critical residues in the ligand-binding pocket of GPR97 and increase the affinity of the ligand for GPR97. Furthermore, the community network analysis suggests that the palmitoylation of Go not only allosterically strengthens the internal interactions between Gαo and Gβγ, but also enhances the coupling between Go and GPR97. Our study provides mechanistic insights into the regulation of aGPCRs via post-translational modifications of the Go protein, and offers guidance for future drug design of aGPCRs. [ABSTRACT FROM AUTHOR]

The 2,4,6,8,10,12-Hexanitro-2,4,6,8,10,12-hexaazaisowurtzitane (CL-20) is considered as the most promising energetic materials (EMs) in terms of its detonation performance. Nonetheless, its applications are limited due to high sensitivity and low phase stability. Thermal decomposition behavior especially for the initial reaction pathway determines its reactivity and sensitivity. An in-depth discernment of the innate decomposition pathways of CL-20 would facilitate the precision tailoring and augmentation of its performance. The thermal behavior and decomposition mechanisms of CL-20 are largely dependent on the experimental conditions and chemical environments. In this brief review, the effects of those factors on the thermal decomposition mechanisms of CL-20 are summarized from both theoretical and experimental perspectives. In particular, the interaction mechanisms between CL-20 and the other commonly used energetic compounds are simultaneously elucidated. • Environmental conditions and contact materials influence the thermal decomposition mechanism of CL-20. • High temperatures can weaken the influence of physical factors on the decomposition of CL-20. • The influence of contact materials on the decomposition mechanism of CL-20 varies depending on the material used. • Need to strengthen theoretical research on the decomposition mechanism of CL-20 under chemical environments. [ABSTRACT FROM AUTHOR]

Piceatannol (PIC) and epigallocatechin gallate (EGCG) are polyphenolic compounds with applications in the treatment of various diseases such as cancer, but their stability is poor. β-lactoglobulin (β-LG) is a natural carrier that provides a protective effect to small molecule compounds and thus improves their stability. To elucidate the mechanism of action of EGCG, PIC, and palmitate (PLM) in binding to β-LG individually and jointly, this study applied molecular docking and molecular dynamics simulations combined with in-depth analyses including noncovalent interaction (NCI) and binding free energy to investigate the binding characteristics between β-LG and compounds of PIC, EGCG, and PLM. Simulations on the binary complexes of β-LG + PIC, β-LG + EGCG, and β-LG + PLM and ternary complexes of (β-LG + PLM) + PIC, (β-LG + PLM) + EGCG, β-LG + PIC) + EGCG, and (β-LG + EGCG) + PIC were performed for comparison and characterizing the interactions between binding compounds. The results demonstrated that the co-bound PIC and EGCG showed non-beneficial effects on each other. However, the centrally located PLM was revealed to be able to adjust the binding conformation of PIC, which led to the increase in binding affinity with β-LG, thus showing a synergistic effect on the co-bound PIC. The current study of β-LG co-encapsulated PLM and PIC provides a theoretical basis and research suggestions for improving the stability of polyphenols. [ABSTRACT FROM AUTHOR]

The Rho family GTPases are crucial drivers of tumor growth and metastasis. However, it is difficult to develop GTPases inhibitors due to a lack of well‐characterized binding pockets for compounds. Here, through molecular dynamics simulation of the RhoA protein, a groove around cysteine 107 (Cys107) that is relatively well‐conserved within the Rho family is discovered. Using a combined strategy, the novel inhibitor DC‐Rhoin is discovered, which disrupts interaction of Rho proteins with guanine nucleotide exchange factors (GEFs) and guanine nucleotide dissociation inhibitors (GDIs). Crystallographic studies reveal that the covalent binding of DC‐Rhoin to the Cys107 residue stabilizes and captures a novel allosteric pocket. Moreover, the derivative compound DC‐Rhoin04 inhibits the migration and invasion of cancer cells, through targeting this allosteric pocket of RhoA. The study reveals a novel allosteric regulatory site within the Rho family, which can be exploited for anti‐metastasis drug development, and also provides a novel strategy for inhibitor discovery toward "undruggable" protein targets. [ABSTRACT FROM AUTHOR]

• PVAc could be dissolved in CO 2 when the pressure was much higher than 30 MPa. • Cosolvents could decrease the transition points of PVAc in CO 2. • The mixtures of CO 2 and cosolvents have the solubility parameters close to PVAc. • The LA-LB interactions are the main influence factor of PVAc dissolving in CO 2. • The generated new interactions by cosolvents have great influence. The dissolution behavior of polymers in CO 2 has become increasingly important to the applications of CO 2 in industry. Experimental results showed that PVAc could be dissolved in CO 2 at a high pressure. When cosolvents such as ethanol, acetic acid, and ethyl acetate were present in the system, the transition points could be decreased with the increase in cosolvent concentration. In this work, the influence mechanisms of cosolvents on dissolution behaviors of PVAc in supercritical CO 2 were investigated by molecular dynamics simulation methods. First, the cohesive energy and solubility parameters of PVAc, cosolvents and CO 2 were analyzed. Compared with CO 2 , the mixtures of CO 2 and cosolvents have closer solubility parameters with PVAc to enhance the dissolubility of PVAc within them. Moreover, the mechanism of PVAc dissolution in CO 2 and the effects of cosolvents on decreasing the transition points were investigated. The Lewis acid–Lewis base (LA-LB) interactions between O atoms in PVAc and C atoms in CO 2 are the main influencing factors of PVAc dissolution in CO 2. The presence of cosolvent can generate new interactions, such as hydrogen bonding and LA-LB interactions, which have different influences on the LA-LB interactions between PVAc and CO 2. Ethanol and ethyl acetate have no great influence on these LA-LB interactions, while acetic acid exerts considerable influence. [ABSTRACT FROM AUTHOR]

• Aqueous nano-film evaporation is studied by molecular dynamics simulation. • The external electric field on the evaporation of the aqueous nano-film is focused in this work. • Aqueous film evaporation was enhanced using a high electric field parallel to the surface of aqueous film. In this work, molecular dynamics simulation has been applied to investigate the influence of external electric field on the evaporation of the aqueous nano-film. The evaporation of the aqueous nano-film with 2240 water molecules and 50 NaCl on a gold (1 0 0) surface is analyzed at the electric fields with various intensities (0, 0.05, 0.1, 0.2 and 0.3 V nm−1) and directions. The predictions show that the evaporation of aqueous film is remarkably enhanced when the electric field E x = 0.2 or 0.3 V nm−1 is parallel to the aqueous film surface. It is also noted that free ions in the aqueous film are accelerated under the action of the higher E x and water molecules in the hydration shell move together with the ions due to the hydration effect. As a result, the interaction between water molecules decreases, which is responsible for increasing the evaporation of the aqueous film under the action of the higher E x. While applying the electric field E y = ±0.3 V nm−1 perpendicular to the aqueous film, ions cannot be in accelerated motion due to the existence of a solid-liquid interface and a liquid-gas surface in y -direction. Therefore, the evaporation enhancement is much lower than that of the aqueous film under the action of the E x. [ABSTRACT FROM AUTHOR]

Carbon nanotube (CNT)/graphene nanostructure has the potential to extend the superior mechanical, thermal, and electrical properties of graphene from two dimensions to three. While the theoretical investigation of CNT/graphene nanostructure based on atomistic modeling is garnering great attention, an open-source numerical tool to generate covalently bonded CNT/graphene junctions is still in lack for material scientists. In this work, a pathfinding algorithm is used to exhaust all possible configurations on graphene to seamlessly connect to a given CNT. The least squares approach method follows to sort out the configuration with minimum energy. The combined methods are able to generate CNT/graphene junction for any CNT type (m, n). Molecular dynamics simulation further reveals that the formed junctions are thermodynamically stable, and thus ready to serve as basic block for a CNT/graphene network. By providing an easy-to-use numerical tool in the form of MATLAB code, the intention is to free material scientists from the tedious preparation of atomic configuration. [ABSTRACT FROM AUTHOR]

• The { 11 2 ¯ 1 } twin embryo is composed of a group of pyramidal stacking faults (PSFs) with 6 d { 11 2 ¯ 1 } or 8 d { 11 2 ¯ 1 } caused by successive slip of partial dislocations with the Burgers vector of 1 36 < 11 2 ¯ 6 ¯ > M . • The growth of { 11 2 ¯ 1 } twin can be carried out by the slip of twinning dislocations (TDs) b ⇀ 1 = 1 6 (4 γ 2 + 1) < 1 ¯ 1 ¯ 26 > ± 1 2 < 1 1 ¯ 00 >. • The interfacial structures of { 11 2 ¯ 1 } twins have the terraced character with short coherent (11 2 ¯ 2)||(11 2 ¯ 0) facets and coherent TB segments, and (0001)||(11 2 ¯ 4) facets. • The { 11 2 ¯ 2 }-{ 11 2 ¯ 1 } double twin structure can form through the dissociation of the TD b ⇀ 1 (11 2 ¯ 2) at the { 11 2 ¯ 2 } twin tip or by the interaction between a basal < a > dislocation and a { 11 2 ¯ 2 } twin boundary (TB). • The coherent twin interfaces can form at their intersected interfaces after formation of { 11 2 ¯ 2 }-{ 11 2 ¯ 1 } double twin structure. The { 11 2 ¯ 1 } twinning and { 11 2 ¯ 2 }-{ 11 2 ¯ 1 } double twinning mechanisms in pure Ti are systematically investigated using molecular dynamics (MD) simulations. MD simulation results indicate that a { 11 2 ¯ 1 } twin embryo is composed of a group of pyramidal stacking faults (PSFs) with 6 d { 11 2 ¯ 1 } or 8 d { 11 2 ¯ 1 } , caused by the successive slip of partial dislocations with the Burgers vector of 1 36 〈 11 2 ¯ 6 ¯ 〉 M. The migration of { 11 2 ¯ 1 } twin boundaries (TBs) is mainly carried out by the slip of twinning dislocations (TDs) b ⇀ 1 = 1 6 (4 γ 2 + 1) < 1 ¯ 1 ¯ 26 > ± 1 2 < 1 1 ¯ 00 >. Two { 11 2 ¯ 2 }-{ 11 2 ¯ 1 } double twinning mechanisms are discovered. One is that a { 11 2 ¯ 1 } twin forms and grows at the { 11 2 ¯ 2 } twin tip through the dissociation of the TD b ⇀ 1 (11 2 ¯ 2) at the { 11 2 ¯ 2 } twin tip, forming the { 11 2 ¯ 2 }-{ 11 2 ¯ 1 } double twin structure. The other is that a basal < a > T dislocation interacts with a { 11 2 ¯ 2 } TB, forming a twin embryo composing of a group of PSF with the 6 d { 11 2 ¯ 1 ¯ } and leaving a step at the { 11 2 ¯ 2 } TB, eventually forming the { 11 2 ¯ 2 }-{ 11 2 ¯ 1 } double twin structure. The interfacial structures of { 11 2 ¯ 1 } twins have the terraced character with short coherent (11 2 ¯ 2)||(11 2 ¯ 0) facets and coherent twin boundary (CTB) segments. In addition, (0001)||(11 2 ¯ 4) facets with a disclination dipoles feature can form at twin tips. The coherent twin interfaces form at their intersected interfaces during the { 11 2 ¯ 2 }-{ 11 2 ¯ 1 } double twinning process. Our present findings may provide clues for designing Ti alloys with excellent strength–ductility properties through obtaining a high-volume fraction of coherent interfaces in terms of { 11 2 ¯ 2 }-{ 11 2 ¯ 1 } double twins. [Display omitted] [ABSTRACT FROM AUTHOR]

A Riemannian stochastic representation of model uncertainties in molecular dynamics is proposed. The approach relies on a reduced-order model, the projection basis of which is randomized on a subset of the Stiefel manifold characterized by a set of linear constraints defining, e.g. , Dirichlet boundary conditions in the physical space. We first show that these constraints are, indeed, preserved through Riemannian pushforward and pullback actions to, and from, the tangent space to the manifold at any admissible point. This fundamental property is subsequently exploited to derive a probabilistic model that leverages the multimodel nature of the atomistic setting. The proposed formulation offers several advantages, including a simple and interpretable low-dimensional parameterization, the ability to constraint the Fréchet mean on the manifold, and ease of implementation and propagation. The relevance of the proposed modeling framework is finally demonstrated on various applications including multiscale simulations on graphene-based systems. [ABSTRACT FROM AUTHOR]

Time difference of arrival (TDOA) is widely used in wireless localization systems. Among the enormous approaches of TDOA, high resolution TDOA algorithms have drawn much attention for its ability to resolve closely spaced signal delays in multipath environment. However, the state-of-art high resolution TDOA algorithms still have performance weakness on resolving time delays in a wireless channel with dense multipath effect. In this paper, we propose a novel TDOA algorithm with super resolution based on a multi-dimensional cross-correlation function: the volume cross-correlation function (VCC). Theoretical analyses are provided to justify the feasibility of the proposed TDOA algorithm, and numerical simulations also show an excellent time resolution capability of the algorithm in multipath environment. [ABSTRACT FROM AUTHOR]

The two-dimensional energetic polymer triaminoguanidine–glyoxal (TAGP) has been used in modification of EMs to formation of various hybrid materials for higher density and better stability due to its excellent capability to desensitize high energetic crystals without any energy loss. In this paper, theoretical calculations based on ReaxFF-MD were performed to demonstrate the thermal decomposition mechanisms of TAGP, which has been further proved by experimental results from Pyro-GC/MS analysis. The results show that there are three dominant pathways for the initial decomposition of TAGP, i.e. , the breakage of C-N bond with production of C 2 H 3 ON 2 (most likely to happen), the scission of N-N bond with release of C 2 H 2 ON, and the rupture of N-N bond accompanied with the proton transfer to release C 2 H 3 ON. Therefore, the C 2 H 3 ON 2 , C 2 H 2 ON and C 2 H 3 ON are the dominant initial decomposition products of TAGP, which may gradually transform to the final gaseous products. The experimental results confirmed the presences of these substances. The major final gaseous products of TAGP include N 2 , H 2 , H 2 O, NH 3 , NH 4 , NH 2 , N 2 H, N 2 H 2 , HCN and CO 2 , among which the concentration of N 2 is the highest, relatively higher than H 2 , H 2 O and NH 3. Besides, the initial decomposition rate of TAGP largely depends on its MW. The activation energies for formation of C 2 H 3 ON 2 and N 2 under isothermal conditions has been obtained to further illustrate the effect of MW on the decomposition rate. • Three types of typical TAGP structural models have been constructed according to the measured molecular weights. • The detailed decomposition mechanisms of TAGP have been proposed. • Their final thermolysis products have been mutually confirmed by ReaxFF-MD simulations and Pyro-GC/MS experiments. [ABSTRACT FROM AUTHOR]

Droplets impinging on solid surfaces is a common phenomenon. However, the motion of surfaces remarkably influences the dynamical behaviors of droplets, and related research is scarce. Dynamical behaviors of water nanodroplets impinging on translation and vibrating solid copper surfaces were investigated via molecular dynamics (MD) simulation. The dynamical characteristics of water nanodroplets with various Weber numbers were studied at five translation velocities, four vibration amplitudes, and five vibration periods of the surface. The results show that when water nanodroplets impinge on translation surfaces, water molecules not only move along the surfaces but also rotate around the centroid of the water nanodroplet at the relative sliding stage. Water nanodroplets spread twice in the direction perpendicular to the relative sliding under a higher surface translation velocity. Additionally, a formula for water nanodroplets velocity in the translation direction was developed. Water nanodroplets with a larger Weber number experience a heavier friction force. For cases wherein water nanodroplets impinge on vibration surfaces, the increase in amplitudes impedes the spread of water nanodroplets, while the vibration periods promote it. Moreover, the short-period vibration makes water nanodroplets bounce off the surface. [ABSTRACT FROM AUTHOR]

The melting of a solid represents a transition between a solid state in which atoms are localized about fixed average crystal lattice positions to a fluid state that is characterized by relative atomic disorder and particle mobility so that the atoms wander around the material as a whole, impelled by the random thermal impulses of surrounding atoms. Despite the fundamental nature and practical importance of this particle delocalization transition, there is still no fundamental theory of melting and instead one often relies on the semi-phenomenological Lindemann-Gilvarry criterion to estimate roughly the melting point as an instability of the crystal lattice. Even the earliest simulations of melting in hexagonally packed hard discs by Alder and Wainwright indicated the active role of nonlocal collective atomic motions in the melting process, and here we utilize molecular dynamics (MD) simulation to determine whether the collective particle motion observed in melting has a similar geometrical form as those in recent studies of nanoparticle (NP) interfacial dynamics and the molecular dynamics of metastable glass-forming liquids. We indeed find string-like collective atomic motion in NP melting that is remarkably similar in form to the collective interfacial motions in NPs at equilibrium and to the collective motions found in the molecular dynamics of glass-forming liquids. We also find that the spatial localization and extent of string-like motion in the course of NP melting and freezing evolves with time in distinct ways. Specifically, the collective atomic motion propagates from the NP surface and from within the NP in melting and freezing, respectively, and the average string length varies smoothly with time during melting. In contrast, the string-like cooperative motion peaks in an intermediate stage of the freezing process, reflecting a general asymmetry in the dynamics of NP superheating and supercooling. [ABSTRACT FROM AUTHOR]

Abstract: Molecular dynamics simulations were performed to characterize the atomic motions that govern grain boundary migration in a series of twist boundaries. In particular, migration of θ =36.87°Σ5, θ =22.63°Σ13, and θ =40.23° general high angle [001] twist boundaries driven by stored elastic energy in fcc nickel were investigated. Atomic motions during migration were identified as single-atom jumps and multiple-atom collective motions (including general string-like cooperative motions and special four-atom shuffles) using quantitative string measurement, the self-part of the van Hove correlation function, and an angular distribution function. The simulation results confirmed that collective four-atom shuffle motion was the rate controlling atomic motion during migration of the Σ5 twist boundary. Furthermore, simulations showed no correlation between individual four-atom shuffles, suggesting migration was controlled by random shuffles rather than a propagation of kinks along ledges. As grain boundary local symmetry decreased (i.e., from a low Σ boundary to a high Σ boundary), string-like cooperative atomic motions (not collective shuffle motions) became increasingly important. Both random single-atom jumps and general string-like cooperative motions were dominant during migration of a general non-Σ twist boundary. Simulations also showed that the activation energy for grain boundary migration was well correlated with the average string length occurring within the boundary. This implies that grain boundary drifting velocity is sensitive to factors (e.g., external stresses, impurities) that can alter string motions within a boundary. [Copyright &y& Elsevier]

Polycrystalline materials are composites of crystalline particles or "grains" separated by thin "amorphous" grain boundaries (GBs). Although GB5 have been exhaustively investigated at low temperatures, at which these regions are relatively ordered, much less is known about them at higher temperatures, where they exhibit significant mobility and structural disorder and characterization methods are limited. The time and spatial scales accessible to molecular dynamics (MD) simulation are appropriate for investigating the dynamical and structural properties of GBs at elevated temperatures, and we exploit MD to explore basic aspects of GB dynamics as a function of temperature. It has long been hypothesized that GB5 have features in common with glass-forming liquids based on the processing characteristics of polycrystalline materials. We find remarkable support for this suggestion, as evidenced by string-like collective atomic motion and transient caging of atomic motion, and a non-Arrhenius GB mobility describing the average rate of large-scale GB displacement. [ABSTRACT FROM AUTHOR]

Abstract: We generalize a previous study of the atomic motions governing grain boundary migration to consider arbitrary misorientations of [001] tilt boundaries. Our examination of the nature of atomic motions employed three statistical measures of atomic motion: the non-Gaussian parameter, the “dynamic entropy” and the van Hove correlation function. These metrics were previously shown to provide a useful characterization of atomic motions both in glass-forming liquids and strained polycrystalline materials. As before, we find highly cooperative, string-like motion of atoms, but the grain boundary migration itself is a longer timescale process in which atoms move across the grain boundary. These observations are consistent with our previous results for Σ5 [001] tilt boundaries. It is evident from our work that the grain boundary structure and misorientation have a significant influence on the rate of grain boundary migration. [Copyright &y& Elsevier]

Abstract: The atomistic mechanism by which grain boundaries migrate is important for understanding the relationship between their structures and dynamical properties. We perform a series of three-dimensional molecular dynamic simulations of the migration of Σ5 tilt grain boundaries of different inclinations in nickel. We identify the migration mechanism through frequent quenches and analysis of the atomic displacements, local and global excess volume, and stress. The migration mechanism has the following components: local volume fluctuations precede the displacements of 3–4 linear atomic clusters in the direction parallel to the tilt axis which, in turn, are followed by individual atomic hops that are primarily perpendicular to the boundary plane. Excess volume is key to both the volume fluctuations and the atomic hops perpendicular to the boundary plane. The linear, or string-like, atomic motion parallel to the tilt axis also gives rise to a strong anisotropy in the grain boundary self-diffusivity. [Copyright &y& Elsevier]

Abstract: Molecular dynamics simulations of stress-driven grain boundary migration in bicrystal thin films demonstrate that the grain boundary mobility decreases as the films are made thinner. Examination of the surface morphology proves that this effect is not associated with grain boundary grooving. The simulation data demonstrate that the grain boundary mobility is a linear function of the inverse thickness. We present a simple model to explain this effect based upon the fundamental mechanism of grain boundary migration: the collective rearrangement of a large group of atoms. Decreasing system size implies that more of the boundary is near the surface. The presence of the free surface interferes with the collective rearrangement of the atoms during boundary motion and hence slows the migration. A simple heuristic analysis, based on this effect, is consistent with the observed functional dependence of boundary mobility on bicrystal thickness. [Copyright &y& Elsevier]

By combining the spectroscopic quality of a crystalline phase with the outstanding thermal and chemical stability of the matrix glass, nanocrystal‐in‐glass composites (NGCs) exhibit excellent optical properties. However, strong interfacial diffusion occurs during high‐temperature encapsulation, leading to the erosion of the nanocrystals and detrimental effects on the final performance. The control of interfacial diffusion has so far relied on intuition and experience, with the underlying physical mechanisms remaining largely unknown. In this study, through atomistic simulations and experimental verification, we have developed atomic models of NGCs, revealing the dynamic characteristics of the interface and elucidating how the glass structure can regulate the interface diffusion. Finally, we demonstrate how a tunable interface can be achieved through compositional adjustments of the glass matrix. [ABSTRACT FROM AUTHOR]

• The deformation path depends strongly on the uniaxial tensile directions. • An intermediated phase (BCC) was firstly found during the HCP → FCC transformation in titanium. • A new formation path of { 10 1 - 1 } twinning relation through BCC stage was observed in titanium. • The pure-shuffle nucleation mechanism of { 10 1 - 2 } twin was found in titanium. In this work, effects of uniaxial tensile directions on the deformation mechanisms of a hexagonal close-packed (HCP) titanium crystalline were investigated by molecular dynamics simulations. Three uniaxial tensile directions, namely the [ 2 1 - 1 - 0 ], [ 01 1 - 0 ] and [ 0001 ] directions, were studied. When the tensile loading was along the [ 2 1 - 1 - 0 ] direction, the parent HCP phase transformed firstly into the body-centered cubic (BCC) phase following the Pitsch-Schrader orientation relationship (OR), and then transformed either into the face-centered cubic (FCC) phase following the Bain path or back to the HCP phase following different variants of the Pitsch-Schrader OR. The new-forming and matrix HCP structures were in a { 10 1 - 1 } twinning relationship with each other. The newly formed FCC phase was in a prismatic-type (P-type) OR with the HCP matrix and in a basal-type (B-type) relationship with the new-forming HCP structure at individual contacting interface. The FCC/HCP interfaces in the P-type OR was immobile while that in the B-type OR propagated by the slip of Shockley partial dislocations. Both FCC/HCP interfaces in the P-type and B-type ORs were observed under high-resolution transmission electron microscope. With the tensile loading along the [ 01 1 - 0 ] direction, deformation mechanism of the system was dominated by the slip and dissociation of prismatic dislocations. The system stretched along the [ 0001 ] direction deformed mainly through the slip and dissociation of pyramidal dislocations, as well as through the activation of { 10 1 - 2 } twinning by a pure shuffle mechanism. The present investigation can provide clues in designing titanium alloys with both high strength and good plasticity. [ABSTRACT FROM AUTHOR]

• Evaporation enhancement of nano-films is larger at the alternating electric field. • Interaction among water molecules becomes weaker at the alternating electric field. • Evaporation is more significant for the electric field parallel to the film surface. In this work, molecular dynamics simulation has been adopted to investigate the influence of square-wave alternating electric field on the evaporation of pure water and aqueous nano-films. The evaporation of the films with 3360 water molecules and 0, 1.11 and 2.18 mol L−1 NaCl on a hot gold (1 0 0) surface was analyzed. The results showed that both the evaporation of water and aqueous films were enhanced by applying the alternating electric field. Compared with the liquid films at the absence of the electric field, the maximum evaporation rates increased 1.71, 1.70 and 1.66 times for water film and aqueous films with 1.11 and 2.18 mol L−1 NaCl for the frequency of 500 GHz, respectively. The reasons were inferred that the water film subjected to the time-varying electrical force resulted in increasing of the rotational and translational kinetic energy of water molecules. Thus applying the alternating electric field accelerated the temperature rise of the water film and enhanced thermal volume expansion of the water film. In addition, the interaction between water molecules became weaker and the water molecules escaped from the water film more easily. The MD simulation also showed that the evaporation enhancement was more significant for the alternating electric field parallel to the films surface than in the perpendicular direction. [ABSTRACT FROM AUTHOR]

In this paper, we observe for the first time that a metastable beta-Zr in the body-centered cubic (BCC) structure can form via a new phase transformation route. The as-received alpha-Zr in the hexagonal closed-packed (HCP) structure transforms partially to the gamma-Zr in the face-centered cubic (FCC) structure via Shockley partial dislocations during deformation, while the gamma-Zr can continuously transform to the beta-Zr by a uniform shear along the 112 FCC direction on the 111 FCC plane during subsequent hot deformation. The beta phase is in a Pitsch–Schrader relationship ((110) BCC | | (0001) HCP , [ 1 1 ¯ 0 ] BCC | | [ 10 1 ¯ 0 ] HCP) with the matrix alpha phase and in a Nishiyama–Wassermann relationship ((110) BCC | | (1 1 ¯ 1 ¯) FCC , [ 1 1 ¯ 0 ] BCC | | [ 12 1 ¯ ] FCC) , with the gamma phase, both of which have not been reported in Zr previously. Combined with corresponding molecular dynamics simulations, the phase transition mechanism and stability of the beta phase are studied. The results show that the beta-Zr phase can be retained in the gamma phase when the cooling is fast enough. [ABSTRACT FROM AUTHOR]

The overexpression of p21-activated kinase 4 (PAK4) is associated with a variety of cancers. In this paper, the binding modes and inhibitory mechanisms of four 7H-pyrrolo[2,3-d]pyrimidine competitive inhibitors of PAK4 were investigated at the molecular level, mainly using molecular dynamics simulations and binding free energy calculations. The results show that the inhibitors had strong interactions with the hinge region, the β-sheets, and the residues with charged side chains around the 4-substituent. The terminal amino group of the inhibitor 5n was different from the other three, which could cause the enhancement of hydrogen bonds or electrostatic interactions formed with the surrounding residues. Thus, inhibitor 5n had the strongest inhibition capacity. The different halogen atoms on the 2-substituents of the inhibitors 5h, 5g, and 5e caused differences in the positions of the 2-benzene rings and affected the interactions of the hinge region. It also affected to some extent the orientations of the 4-imino groups and consequently their affinities for the surrounding charged residues. The combined results lead to the weakest inhibitory capacity of inhibitor 5e. [ABSTRACT FROM AUTHOR]

Monoacylglycerol lipase (MAGL) can regulate the endocannabinoid system and thus becomes a target of antidepressant drugs. In this paper, molecular docking and molecular dynamics simulations, combined with binding free energy calculation, were employed to investigate the inhibitory mechanism and binding modes of four aryl formyl piperidine derivative inhibitors with different 1-substituents to MAGL. The results showed that in the four systems, the main four regions where the enzyme bound to the inhibitor included around the head aromatic ring, the head carbonyl oxygen, the tail amide bond, and the tail benzene ring. The significant conformational changes in the more flexible lid domain of the enzyme were caused by 1-substituted group differences of inhibitors and resulted in different degrees of flipping in the tail of the inhibitor. The flipping led to a different direction of the tail amide bond and made a greater variation in its interaction with some of the charged residues in the enzyme, which further contributed to a different swing of the tail benzene ring. If the swing is large enough, it can weaken the binding strength of the head carbonyl oxygen to its nearby residues, and even the whole inhibitor with the enzyme so that the inhibition decreases. [ABSTRACT FROM AUTHOR]

CH4 can be separated from low-concentration coal bed methane (LCCBM) by using the hydrate-based gas separation (HBGS) method. To study the contribution of different cyclic organic compounds to the separation of CH4 in LCCBM, an LCCBM hydrate model was constructed. Based on the Monte Carlo and molecular dynamics theory, we simulated the effect of three cyclic organic compounds—cyclopentane (CP), cyclopentanone (CP-one), and cyclopentanol (CP-ol)—on the stability of the LCCBM hydrate at P = 2 MPa, various temperatures, and discussed the structural stability of the hydrate in depth in terms of final snapshots, radial distribution function, mean square displacement, diffusion coefficient, and potential energy change. The results showed that for the CH4-N2 LCCMM gas mixture, CP showed the best facilitation effect compared to the other two cyclic compounds by maintaining the stability of the LCCBM hydrate well at T = 293 K. The promotion effect of CP-one is between CP and CP-ol, and when the temperature increases to T = 293 K, the oxygen atoms in the water molecule can maintain the essential stability of the hydrate structure, although the orderliness decreases significantly. Moreover, the structure of the hydrate model containing CP-ol is destroyed at T = 293 K, and the eventual escape of CH4 and N2 molecules in solution occurs as bubbles. The research results are important for further exploration of the mechanism of action of cyclic promoter molecules with LCCBM hydrate molecules and promoter preferences. [ABSTRACT FROM AUTHOR]

Motivation: Hydrogen bonds (H-bonds) play an essential role for many molecular interactions but are also often transient, making visualising them in a flexible system challenging. Results: We provide pyHVis3D which allows for an easy to interpret 3D visualisation of H-bonds resulting from molecular simulations. We demonstrate the power of pyHVis3D by using it to explain the changes in experimentally measured binding affinities for three T-cell receptor/peptide/MHC complexes and mutants of each of these complexes. [ABSTRACT FROM AUTHOR]

In the current study, the effect of hydrogen atoms on the intergranular failure of α-iron is examined by a molecular dynamics (MD) simulation. The effect of hydrogen embrittlement on the grain boundary (GB) is investigated by diffusing hydrogen atoms into the grain boundaries using a bicrystal body-centered cubic (BCC) model and then deforming the model with a uniaxial tension. The Debye Waller factors are applied to illustrate the volume change of GBs, and the simulation results suggest that the trapped hydrogen atoms in GBs can therefore increase the excess volume of GBs, thus enhancing intergranular failure. When a constant displacement loading is applied to the bicrystal model, the increased strain energy can barely be released via dislocation emission when H is present. The hydrogen pinning effect occurs in the current dislocation slip system, <111>{112}. The hydrogen atoms facilitate cracking via a decrease of the free surface energy and enhance the phase transition via an increase in the local pressure. Hence, the failure mechanism is prone to intergranular failure so as to release excessive pressure and energy near GBs. This study provides a mechanistic framework of intergranular failure, and a theoretical model is then developed to predict the intergranular cracking rate. [ABSTRACT FROM AUTHOR]

[Display omitted] • It shows a strong interaction between SCMC and metal surfaces according to the adsorption configuration and binding energy. • The SCMC gets close to the different metal surfaces in water environment as well as the anhydrous conditions. • The interaction energy decreases from SCMC and the metal surfaces compared to no water environment. • The adsorption energy between SCMC and the metal surfaces increases with the increasing polymerization degree of SCMC. Sodium carboxymethyl cellulose (SCMC) is an effective corrosion inhibitor that provides good protection to metal surfaces. This study investigates the corrosion inhibition properties of SCMC on Fe, Cu, and Al using molecular dynamics simulations. The effects of the adsorption configuration, interaction energy of SCMC on different metal surfaces, and the degree of polymerization change of SCMC molecules were analyzed. The results show that under anhydrous conditions, the adsorption energy between the SCMC and the metal surface increases with its degree of polymerization. The SCMC also gets close to the different metal surfaces, and the carboxyl oxygen atoms in the molecular chain of SCMC are mainly distributed at a distance of about 2.9 Å from the metal surface. It illustrates a strong interaction between SCMC and metal surfaces, and the SCMC breaks free from the water molecules and eventually still adsorbs to the metal surface in water environment, but the adsorption energy is reduced by the water environment. [ABSTRACT FROM AUTHOR]

[Display omitted] • Presenting an atomic-scale tribological visualization method to assess whether graphene coatings enhance the tribomechanical properties of substrates. • Atomic force and contact deformation analysis show that the evolution of friction behavior is due to graphene coatings overlaid on different substrates. • Graphene coatings on hard and soft substrates lead to different critical loads. • Enhanced toughness of soft substrates by multilayer graphene. As a two-dimensional material, graphene film is a good solid lubricant candidate for improving the tribomechanical performance of micro-and nano-electromechanical systems. Graphene has a significant impact on protecting the top layer of a substrate from wear and reducing friction. However, the frictional behavior has been found to vary when coating graphene onto different substrates. In the present study, using molecular dynamics (MD) simulations, graphene was deposited as a monolayer coating on the substrate sliding against the diamond tip, which revealed not only significant improvement in tribological behavior by reducing both friction and contact deformation volume, but also notably demonstrated the difference between hard and soft substrate coating with graphene. Under 58.5nN loading, the optimal antifriction effect of graphene coating on Au substrate was 94.2%, with a higher friction indicating a greater indentation depth and greater contact deformation. The contact deformation volume can be used as a standard to measure the surface friction of graphene. Unlike hard Si substrates, monolayer graphene coatings are prone to rupture at 200 nN loads. At low loads, the single graphene coating has the best anti-friction effect on the soft gold substrate, and at higher loads, the graphene on the hard silicon substrate is not prone to rupture, providing continuous and stable lubrication. The study also revealed a tunable toughening mechanism of graphene layers. The mechanism entails a reduction in the volume of substrate contact deformation with the progressive addition of graphene layers. This finding has the potential to enhance the tribological performance of the graphene-coated substrate. [ABSTRACT FROM AUTHOR]

As a new type of pollutants, nanoplastics (NPs), which are easily ingested by humans from food wraps, salt, drinking water, have been widely detected in various water environments, and are a threat to human health. It is therefore urgent to develop an efficient method to remove NPs from the diet or relief its harm. In the present study, the possibility of a well-known human probiotic, lactic acid bacteria (LAB), was evaluated to remove NPs from food as an absorbent. The results indicated that LAB from infant feces could efficiently absorb three types NPs, i.e. polypropylene (PP), polyethylene (PE), and polyvinyl chloride (PVC) with the adsorption rates of PP > PE > PVC (PP 78.57%, PE 71.59%, PVC 66.57%) and the Nile red-stained NPs being aggregated on the surfaces of Lactobacillus cells. The smaller the particle size, the stronger the ability of NP adsorption on the cell surface. The hydrophobicity of NPs and bacterial cells affected the adsorption process. The measurement of adsorption rates of different cell components indicated that the overall adsorption effect of cell was better than that of individual cell component. The results of molecular dynamics analysis revealed that adsorption was mainly caused by electrostatic interactions, van der Waals forces, and hydrogen bonds. The hydrophobic interaction was also involved in adsorption process. Overall, this research may provide new information for developing new strategies for NPs removal in intestinal environment. [Display omitted] • Lactic acid bacteria from infant feces could efficiently absorb nanoplastics. • The Nile red-stained nanoplastics were aggregated on the surfaces of bacterial cells. • The hydrophobic forces were involved in the nanoplastics adsorption. • The overall adsorption effect of cell was better than that of single cell component. • The adsorption forces were H-bonds, electrostatic and van der Waals forces. [ABSTRACT FROM AUTHOR]

Previous atomistic simulations of hydrogen embrittlement in bcc iron have provided atomistic mechanisms for crack propagation and been used to develop predictive models. In order to bridge the nano-scale simulations to realistic field operations, in current study molecular dynamics (MD) simulations were first used to predict a hydrogen concentration that corresponds to ductile to brittle transition (DTB). The estimated hydrogen concentration was then used to assess the critical hydrogen concentration that induces DTB transition in experimental specimens. Apparently, the calculated critical hydrogen concentration is much larger than the actual concentration found in pipeline steel under routine operations. Recent experiments found that while the presence of minor cycles (i.e., R = K min / K max > 0.9) in underload spectra would only make small contribution to crack propagation in air, they could enhance crack growth significantly in the presence of hydrogen atoms. Therefore, it is reasonable to expect that minor cycles have a significant effect on accumulating hydrogen atoms in the plastic zone and inducing a DTB transition in the aqueous environment where diffusible hydrogen atoms can be generated. Based on this hypothesis, the theoretical critical hydrogen value obtained from atomistic simulation was then used to calculate the number of hydrogen atoms required to saturate the plastic zone. Furthermore, the number of minor cycles required to accumulate hydrogen atoms to cause a DTB transition could be assessed. The prediction based on this model and experimental results are in good agreement. The atomistic mechanism for DTB due to the accumulation of hydrogen during cyclic loading validated in current study implies the importance of the loading spectrum in hydrogen-assisted cracking. [ABSTRACT FROM AUTHOR]

Abstract: Molecular dynamics (MD) simulation has broad applications, and an increasing amount of computing power is needed to satisfy the large scale of the real world simulation. The advent of the many-core paradigm brings unprecedented computing power, but it remains a great challenge to harvest the computing power due to MD’s irregular memory-access pattern. To address this challenge, this paper presents a joint application/architecture study to enhance the scalability of MD on Godson-T-like many-core architecture. First, a preprocessing approach leveraging an adaptive divide-and-conquer framework is designed to exploit locality through memory hierarchy with software controlled memory. Then three incremental optimization strategies–a novel data-layout to improve data locality, an on-chip locality-aware parallel algorithm to enhance data reuse, and a pipelining algorithm to hide latency to shared memory–are proposed to enhance on-chip parallelism for Godson-T many-core processor. Experiments on Godson-T simulator exhibit strong-scaling parallel efficiency of 0.99 on 64 cores, which is confirmed by a field-programmable gate array emulator. Also the performance per watt of MD on Godson-T is much higher than MD on a 16-cores Intel core i7 symmetric multiprocessor (SMP) and 26 times higher than MD on an 8-core 64-thread Sun T2 processor. Detailed analysis shows that optimizations utilizing architectural features to maximize data locality and to enhance data reuse benefit scalability most. Furthermore, a hierarchical parallelization scheme is designed to map the MD algorithm to Godson-T many-core cluster and a simple performance model is derived, which suggests that the optimization scheme is likely to scale well toward exascale. Certain architectural features are found essential for these optimizations, which could guide future hardware developments. [Copyright &y& Elsevier]

Abstract: Molecular dynamics simulations were performed to investigate the hydrogen interaction with edge dislocations during deformation in α-Fe. In particular, uniaxial tensile tests of a single crystal iron were conducted after the single crystal was plastically deformed to introduce high density of edge dislocations and was doped with different levels of lattice hydrogen concentration. During system relaxation, hydrogen atoms have tendency to diffuse and stay around dislocation line – a well-known hydrogen trap-site in α-Fe. Our simulations show that the yield strength of the bcc iron is very sensitive to the presence of hydrogen within edge dislocations, i.e., it increases as hydrogen concentration increases. After yielding, hydrogen atoms are de-associated with the moving dislocations, suggesting that the yield strength enhancement is caused by the hydrogen pinning effect. This direct observation of hydrogen hardening effects has confirmed the experimental findings by Matsui, etc. Additional simulations also indicate that hydrogen interaction with edge dislocations is sensitive to temperature as well as vacancies around dislocation core. [Copyright &y& Elsevier]

The incorporation of additive into rubber matrix is a promising approach toward desirable damping materials. However, the design and selection of additives remain a challenge. Herein, tetraphenylphenyl-modified damping additives were synthesized by Diels-Alder chemistry. The effects of additives on the mechanical and morphological properties of phenyl silicone rubber were investigated experimentally and computationally. Experimental results showed that the addition of additives substantially improved the damping while preserving excellent mechanical properties. The composite with 15 phr tetraphenylphenyl-modified dimethylpolysiloxane (TPP-VMPS-3) exhibited a broad plateau of loss factor (tanδ >0.25) from −50 to 30 °C, effectively expanding the damping temperature range. When the composite incorporated 15 phr tetraphenylphenyl-modified methylphenylpolysiloxane (TPP-VPMPS), the tanδ increased from 0.09 to 0.21 at 150 °C, showing excellent high-temperature damping performance. Furthermore, molecular dynamics (MD) simulation provided mechanistic insights into the phase separation and relaxation behavior of composites by studying the compatibility, interaction mechanism, and diffusion characteristic. The results demonstrated that the enhanced intermolecular interactions and steric hindrance were the crucial reason for the improvement of damping. This work shed light on the relationship among composition, structure and property, which may provide a framework for preparing high-performance silicone composites via the synergistic experimental and computational method. [Display omitted] • Tetraphenylphenyl-modified damping additives were synthesized by Diels-Alder chemistry. • The enhanced intermolecular interaction and steric hindrance were the crucial reason for the improvement of damping. • The simulation results elucidated the molecular mechanism of phase separation and relaxation behavior. [ABSTRACT FROM AUTHOR]

The development of multifunctional and miniaturized electronic devices requires the related materials to possess higher dielectric constant (DC), lower dielectric loss, and higher thermal conductivity. In this study, first, five functional groups are selected to modify graphene and determine the most favourable functional group to increase the DC of graphene/carboxylated acrylonitrile butadiene rubber systems by molecular dynamics (MD) simulation. Second, polymer polyethyleneimine (PEI) with different structure and molecular weight is used to reduce graphene oxide simultaneously in experiments. The results show that branched PEI helps to enhance DC values. In addition, the linear low molecular weight PEI assists in the mechanical and thermal performances, whereas linear high molecular weight PEI synchronously improves the dielectric, mechanical, and thermal performances. Subsequently, the combination of experiments and MD simulations provides in-depth insight into the mechanism and influencing factors for the ameliorative properties. The simulation results indicate that the meliorated dielectric, thermal, and mechanical properties of composites are mainly related to the interface behaviour, including interface compatibility, interface bonding strength, interface phonon vibration power spectrum, and interface hydrogen bonds. This research provides a theoretical basis to prepare high-performance composites required in the application of electronic devices. Unlabelled Image • A computational method that suitable for calculating the dielectric constant values of GO/XNBR composites was established. • A reasonable interface structure of modified GO/XNBR composite is designed and verified by means of experiment results. • An in-depth understand of the performance of GO/XNBR composites was given via molecular simulation methods. [ABSTRACT FROM AUTHOR]

• With the increase of grafting ratio, the solubility parameter of carbon nanotubes (SWCNTs) first decrease, reach a minimum and then increase. • The SWCNTs with different functional groups exhibit different compatibility behaviors with styrene butadiene rubber (SBR). • Each functional group has the optimum grafting ratio at which the compatibility is the best. From the perspective of thermodynamics, the compatibility between filler and matrix determines the dispersion and morphology of filler and further determines the final properties of composites. At present, it is difficult to obtain a quantitative relationship between the surface chemistry of filler and compatibility with matrix through experimental means. In this study, the quantitative relationship between functional groups and Hildebrand (δ T) and two-component solubility parameters (δ vdW , δ ele) of single-walled carbon nanotubes (SWCNTs) was obtained by molecular dynamics (MD) simulation. The most notable conclusion is that with the increase of grafting ratio, the δ T and δ vdW of SWCNTs first decrease, reach a minimum and then increase. This regularity makes the SWCNTs with different functional groups exhibit different compatibility behaviors with styrene butadiene rubber (SBR), resulting in different functionalization principles for different groups. Two-component solubility parameters of SWCNTs and SBR were further proved to be able to predict well their compatibility by Flory-Huggins model. Each functional group has the optimum grafting ratio at which the compatibility is the best. Additionally, the –CH 3 , –CH(O)CH– and –OH functionalized systems exist the optimum temperature for the best compatibility. The multifunctional groups is superior to a single group for the compatibility. This study provides a quantitative guidance for the functionalization of SWCNTs towards the good compatibility with SBR. [ABSTRACT FROM AUTHOR]

Lung cancer is the most frequent cause of cancer-related deaths worldwide, and mutations in the kinase domain of the epidermal growth factor receptor (EGFR) are a common cause of non-small-cell lung cancers, which is a major subtype of lung cancers. Recently, a series of 5-methylpyrimidine-pyridinone derivatives have been designed and synthesized as novel selective inhibitors of EGFR and EGFR mutants. However, the binding-based inhibition mechanism has not yet been determined. In this study, we carried out molecular dynamic simulations and free-energy calculations for EGFR derivatives to fill this gap. Based on the investigation, the three factors that influence the inhibitory effect of inhibitors are as follows: (1) The substitution site of the Cl atom is the main factor influencing the activity through steric effect; (2) The secondary factors are repulsion between the F atom (present in the inhibitor) and Glu762, and the blocking effect of Lys745 on the phenyl ring of the inhibitor. (3) The two factors function synergistically to influence the inhibitory capacity of the inhibitor. The theoretical results of this study can provide further insights that will aid the design of oncogenic EGFR inhibitors with high selectivity. [ABSTRACT FROM AUTHOR]

Recently, ZnS quantum dots have attracted a lot of attention since they can be a suitable alternative for cadmium-based quantum dots, which are known to be highly carcinogenic for living systems. However, the structural stability of nanocrystalline ZnS seems to be a challenging issue since ZnS nanoparticles have the potential to undergo uncontrolled structural change at room temperature. Using the molecular dynamics technique, we have studied the structural evolution of 1 to 5 nm freestanding ZnS nanoparticles with zinc-blende and wurtzite crystal structures. Simulation results revealed that relaxed configurations of ZnS nanoparticles larger than 3 nm consist of three regions: a) a crystalline core, b) a distorted network of 4-coordinated atoms environing the crystalline core, and c) a surface structure made entirely of 3-coordinated atoms. Decreasing the size of ZnS nanoparticle to 2 nm will cause the crystalline core to disappear. Further reducing the size will cause all of the atoms to become 3-coordinated. Dipole moments of zinc-blende and wurtzite nanoparticles are in the same range when the nanoparticles are smaller than 3 nm. Increasing the size makes dipole moments converge to the bulk values. This makes zinc-blende and wurtzite nanoparticles less and more polar, respectively. [ABSTRACT FROM AUTHOR]