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Clean oxide surfaces are generally hydrophilic. Water molecules anchor at undercoordinated surface metal atoms that act as Lewis acid sites, and they are stabilized by H bonds to undercoordinated surface oxygens. The large unit cell of In2O3(111) provides surface atoms in various configurations, which leads to chemical heterogeneity and a local deviation from this general rule. Experiments (TPD, XPS, nc-AFM) agree quantitatively with DFT calculations and show a series of distinct phases. The first three water molecules dissociate at one specific area of the unit cell and desorb above room temperature. The next three adsorb as molecules in the adjacent region. Three more water molecules rearrange this structure and an additional nine pile up above the OH groups. Despite offering undercoordinated In and O sites, the rest of the unit cell is unfavorable for adsorption and remains water-free. The first water layer thus shows ordering into nanoscopic 3D water clusters separated by hydrophobic pockets.

Photoinjected excess electrons (EEs) can fulfill the direct reduction of CO2 (CO2R) in an aqueous solution. However, the underlying mechanism is still poorly understood, especially the EE dynamics, which govern reaction mechanisms. Here, using a hybrid functional‐based ab initio molecular dynamic simulation strategy, it accurately characterizes the dynamics details of CO2R by aqueous EEs in solution and uncovers the nature of how EEs migrate for efficient CO2R. The AIMD simulations reveal that the injected EEs undergo hydration with diverse hydrated forms (various pre‐hydrated/e−pre/e22−pre and hydrated/e−aq/e22−aq) and multiple reaction channels due to competition of hydration versus migration. Interestingly, all pathways go through the same relay state [CO22−]aq and reach the same product (HCOO−). The core process before [CO22−]aq is competitive electron hydration and possible e−pre‐migration featuring either slowly flowing or fast jumping mode, while that after [CO22−]aq is proton transfer catalyzed by H‐bonding network as a proton source. The nature is how the concerted hydration dynamics of EEs and target CO2 govern the reaction proceeding through modulating their energy gap. This study provides dynamics insights into CO2R in aqueous solution by diverse e−pre/e−aq and the proposed strategy can also be utilized to explore the reduction mechanisms based on pre‐solvated electrons in other media. [ABSTRACT FROM AUTHOR]

The transition from lithium‐based energy storage to post lithium systems plays a crucial part in achieving an environmentally sustainable energy infrastructure. Prime candidates for the replacement of lithium are sodium and potassium batteries. Despite being critical to battery performance, the solid electrolyte interphase (SEI) formation process for Na and K batteries remains insufficiently understood, especially compared to the well‐established lithium systems. Using ab initio molecular dynamics (AIMD) simulations based on density functional theory (DFT) calculations, we study the first steps of SEI formation upon the decomposition of typical solvent molecules on lithium, sodium and potassium metal anodes. We find that two dominant products form during the early SEI formation of cyclical carbonates on alkali metal anodes, carbon monoxide and alkali‐carbonate. The carbonate‐producing reaction is thermodynamically favorable for all tested metals, however, Na and K exhibit a much stronger selectivity than Li towards carbonate formation. Furthermore, we propose a previously unknown reaction mechanism for the CO polymerization on metallic lithium. [ABSTRACT FROM AUTHOR]

The potential energy surface (PES) has been explored for BSinGe4−n+ (n = 0−2) systems using density functional theory (DFT). The global minima (1a, 1b, and 1c) of the considered systems contain a planar tetracoordinate boron (ptB) center. The neutral states of the systems do not have a ptB in the global minimum structures. The designed BGe4+, BSiGe3+, and BSi2Ge2+ systems have 18 valence electrons. The CCSD(T)/aug-cc-pVTZ level of theory has been applied to compute the relative energies of the low-lying isomers with respect to the global minima. The dynamical stability of BSinGe4−n+ (n = 0−2) systems is confirmed from the atom-centered density matrix propagation (ADMP) simulation over 20 ps of time at temperatures of 300 K and 500 K. The natural charge computations show that the charges on the ptB are highly negative, indicating strong σ-acceptance from the peripheral atoms. The 1a, 1b, and 1c structures of BGe4+, BSiGe3+, and BSi2Ge2+ systems, respectively, have σ/π-dual aromaticity as predicted from the nucleus-independent chemical shift (NICS) values. Density functional theory (DFT) based computation predicts the presence of a planar tetracoordinate boron (ptB) in the global minimum energy structures of BSinGe4−n+ (n = 0−2) systems. The systems are kinetically stable and show σ- and π- electronic delocalization. [ABSTRACT FROM AUTHOR]

Proton conductors are promising materials for clean energy, but most available materials exhibit sufficient conductivity only when chemically substituted to create oxygen vacancies, which often leads to difficulty in sample preparation and chemical instability. Recently, proton conductors based on hexagonal perovskite‐related oxides have been attracting attention as they exhibit high proton conductivity even without the chemical substitutions. However, their conduction mechanism has been elusive so far. Herein, taking three types of oxides with different stacking patterns of oxygen‐deficient layers (β‐Ba2ScAlO5, α‐Ba2Sc0.83Al1.17O5, and BaAl2O4) as examples, the roles of close‐packed double‐octahedral layers and oxygen‐deficient layers in proton conduction are shown. It is found that "undoped" β‐Ba2ScAlO5, which adopts a structure having alternating double‐octahedral layer and double‐tetrahedral layer with intrinsically oxygen‐deficient hexagonal BaO (h') layer, shows high proton conductivity (≈10−3 S cm−1 above 300 °C), comparable to representative proton conductors. In contrast, the structurally related oxides α‐Ba2Sc0.83Al1.17O5 and BaAl2O4 exhibit lower conductivity. Ab initio molecular dynamics simulations revealed that protons in β‐Ba2ScAlO5 migrate through the double‐octahedral layer, while the h′ layer plays the role of a "proton reservoir" that supplies proton carriers to the proton‐conducting double‐octahedral layers. The distinct roles of the two layers in proton conduction provide a strategy for developing high‐performance proton conductors. [ABSTRACT FROM AUTHOR]

Based on static DFT calculations and AIMD simulations, the stable outer- and inner-sphere adsorption complexes are respectively formed through hydrogen bonding and coordinate bonding with aluminol groups of the kaolinite(0 0 1) surface. The most stable inner-sphere complexes are predicted to be tridentate surface complexes with an eight-folded coordination structure in the first coordination sphere of Am3+. [Display omitted] • Adsorption of Am3+ and Am(OH)2+ aqua ions at the kaolinite(0 0 1)-water interface is investigated by static DFT and AIMD simulations. • Stable outer- and inner-sphere Am(III) adsorption complexes are identified, highlighting the role of hydrogen bonding and coordinate bonding with surface aluminol groups. • A tridentate, eight-folded coordination structure for the most stable Am(III) inner-sphere complexes is predicted across a pH range of 5.5–7. • The efficiency and accuracy of combining static DFT calculations for initial screening and AIMD simulations for comprehensive dynamic analysis are demonstrated. Understanding the structures and stabilities of actinide species is crucial for comprehending the sorption mechanisms at mineral–water interfaces. However, the relevant molecular-level fundamental aspects of actinide coordination chemistry at the mineral–water interface remain unclear. We herein conduct a systematic theoretical study of coordination structures and adsorption energies of Am3+ and Am(OH)2+ sorption complexes at the kaolinite(0 0 1)-water interface by integrating static density functional theory (DFT) calculations and ab initio molecular dynamics (AIMD) simulations. Computational results show that stable outer- and inner-sphere adsorption complexes are respectively formed through hydrogen bonding and coordinate bonding with surface aluminol groups. The most stable inner-sphere species are predicted to be tridentate surface complexes with an eight-folded coordination structure in the first coordination sphere of Am(III). This work deepens the understanding of Am(III) adsorption and complexation behaviors at the mineral–water interface, providing essential insights for actinide migration in natural environments and nuclear waste disposal. The synergy between static DFT calculations for initial screening and AIMD simulations for comprehensive dynamic analysis in this work enhances the efficiency and accuracy of theoretical predictions for actinide environmental chemistry and can be helpful for the broader research fields of geochemistry and environmental science. [ABSTRACT FROM AUTHOR]

As phase change materials (PCMs), Sb–Te based alloys have received a lot of attention in recent years. However, the mechanism for the formation of the alloy and its application as PCMs is not fully understood. The high-throughput First-principles calculations and melt-quench ab initio molecular dynamics simulations were adopted to explore the microstructure and properties of Sb–Te alloys in this work. The hetero-atomic interaction and disordered distribution make Sb–Te alloy with layered microstructure more stable. Although Sb1−xTex solid solution is the metastable phase, it is still stable for PCMs in the certain ranges of solid solubility (0.4

Recent advancements in battery technology emphasize the critical role of solid electrolytes in enhancing the performance and safety of next-generation batteries. In this study, we investigate the interface stability and reaction mechanisms of Li 3 YCl 5 Br, a promising halide-based solid electrolyte, in contact with high-voltage Ni-Mn-Co (NMC) cathodes and a Li metal anode using ab initio molecular dynamics simulations. Our findings reveal that Li 3 YCl 5 Br reacts with charged NMC cathodes. This reaction involves changes in the oxidation states of Br - anions in Li 3 YCl 5 Br and d-element cations in NMC, as well as the diffusion of Li ions from the solid electrolyte to the cathode to maintain charge balance. The reaction is confined to the interface, suggesting bulk stability. Conversely, the Li/Li 3 YCl 5 Br interface exhibits significant instability, with a chemical reaction that results in substantial structural changes and the formation of LiCl and LiBr at the solid electrolyte surface and metallic Y at the Li anode surface. These insights provide valuable information for optimizing interfacial design, aiming at improving the performance and reliability of all-solid-state batteries using halide solid electrolytes.

Density functional theory (DFT) is used to explore the structure, stability, and bonding in CSiGaAl2−/0 and CGeGaAl2−/0 systems having planar tetracoordinate carbon (ptC). The neutral systems have 17 valence electrons and the mono‐anionic systems have 18 valence electrons. The ab initio molecular dynamics simulations for 2000 fs time at two different temperatures (300 and 500 K) supported the kinetic stability of the systems. From the natural bond orbital (NBO) analysis it is shown that there is a strong electron donation from the ligand atoms to the ptC atom. We have used Li+ ion for the neutralization of the mono‐anionic systems and more interestingly it does not disrupt the planar structure. The most preferable site for binding of Li+ ion is along the AlAl bond in both of the mono‐anionic systems. All the systems in this work have both σ and π aromaticity which is predicted from the computations of nucleus independent chemical shift (NICS). Although the anionic species obey the 18 valence electronic rule, the neutral systems break the rule with 17 valence electrons. However, both sets of systems are stable in the planar form. The bonding analysis of the systems includes molecular orbital, adaptive natural density partitioning (AdNDP), quantum theory of atoms in molecules (QTAIM), electron localization function (ELF) basin, and aromaticity analyses. The energy decomposition analysis (EDA) determines the interaction of Li+ ion with CSiGaAl2− and CGeGaAl2− in Li@SiGaAl2 and Li@GeGaAl2, respectively. [ABSTRACT FROM AUTHOR]

Developing new soft magnetic amorphous alloys with a low cost and high saturation magnetization (Bs) in a simple alloy system has attracted substantial attention for industrialization and commercialization. Herein, the glass-forming ability (GFA), thermodynamic properties, soft magnetic properties, and atomic structures of Fe80+xSi5−xB15 (x = 0–4) amorphous soft magnetic alloys were investigated by ab initio molecular dynamics (AIMD) simulations and experiments. The pair distribution function (PDF), Voronoi polyhedron (VP), coordination number (CN), and chemical short- range order (CSRO) were analyzed based on the AIMD simulations for elucidating the correlations between the atomic structures with the glass-forming ability and magnetic properties. For the studied compositions, the Fe82Si3B15 amorphous alloy was found to exhibit the strongest solute–solute avoidance effect, the longest Fe-Fe bond, a relatively high partial CN for the Fe-Fe pair, and the most pronounced tendency to form more stable clusters. The simulation results indicated that Fe82Si3B15 was the optimum composition balancing the saturation magnetization and the GFA. This prediction was confirmed by experimental observations. The presented work provides a reference for synthesizing new Fe-Si-B magnetic amorphous alloys. [ABSTRACT FROM AUTHOR]

It is a paradigm in chemistry that chemical reactions are mainly governed by thermodynamics. Within this assumption, reaction rates can be derived from transition state theory which requires a quasi-equilibrium between reactants and activated transition state complexes that is achieved through friction. However, to reach thermal equilibrium through friction takes some time. Here we show, based on ab initio molecular dynamics simulations of the interaction of molecular oxygen with stepped Pt surfaces, that chemical reactions in heterogeneous catalysis can occur in a non-equilibrium fashion when the excess kinetic energy upon entering the potential well of a reaction intermediate is large enough.

The scaling behavior of ab initio molecular dynamics simulations for the different size bulk systems of liquid methanol is presented and thereby the characteristics of every system performing on either a local compute cluster or a supercomputer are analyzed. Additionally, the influence of different parameters on the quality of the infrared and Raman spectra is investigated using different simulation frameworks, including time step, convergence criteria, density functional approximation, and basis set. Both the maximally localized Wannier functions and the radical Voronoi tessellation approaches are employed to evaluate vibrational spectra from the trajectories. The results of infrared and Raman spectra are classified in two frequency regions, 500 to 1600 cm−1 and 2500 to 4000 cm−1, in order to compare and discuss the experimental spectra and the results derived from ab initio molecular dynamics simulations comprehensively. The outcome of this study guides future experimental and theoretical researchers in order to acquire a profound perception into vibrational spectra, which evolves the way of elucidating molecular structure. [ABSTRACT FROM AUTHOR]

NV color centers in diamond exhibit a variety of interesting properties which make them suitable for different technological applications, like quantum sensing, secure message encryption and biological imaging. They can also be used as qubits. In order to construct arrays of NV centers for quantum computing, it is necessary to maximize interqubit interactions and, at the same time, minimize all sources of decoherence. This could possibly be achieved by using femtosecond-laser pulses in the production process. In this work, we performed ab initio atomistic simulations to study ultrafast nonthermal NV center formation in diamond induced by excitation through femtosecond-laser pulses. Our results indicate that the interatomic bonding properties can be modified by the excitation in such a way that a vacancy and a nitrogen impurity, initially not nearest neighbors, attract themselves and form a NV center within 250 fs after the excitation. In contrast to the thermal behavior, here, the nitrogen atom starts to oscillate nonthermally between two grid points after the excitation. For comparison to the thermal case we performed a single run in which a NV center is thermally formed at T = 1500 K in one of our supercells. Image 1 [ABSTRACT FROM AUTHOR]

Developing new soft magnetic amorphous alloys with a low cost and high saturation magnetization (Bs) in a simple alloy system has attracted substantial attention for industrialization and commercialization. Herein, the glass-forming ability (GFA), thermodynamic properties, soft magnetic properties, and atomic structures of Fe80+xSi5−xB15 (x = 0–4) amorphous soft magnetic alloys were investigated by ab initio molecular dynamics (AIMD) simulations and experiments. The pair distribution function (PDF), Voronoi polyhedron (VP), coordination number (CN), and chemical short- range order (CSRO) were analyzed based on the AIMD simulations for elucidating the correlations between the atomic structures with the glass-forming ability and magnetic properties. For the studied compositions, the Fe82Si3B15 amorphous alloy was found to exhibit the strongest solute–solute avoidance effect, the longest Fe-Fe bond, a relatively high partial CN for the Fe-Fe pair, and the most pronounced tendency to form more stable clusters. The simulation results indicated that Fe82Si3B15 was the optimum composition balancing the saturation magnetization and the GFA. This prediction was confirmed by experimental observations. The presented work provides a reference for synthesizing new Fe-Si-B magnetic amorphous alloys.

The effects on the lattice structure and electronic properties of different polymorphs of silver halide, AgX (X = Cl, Br, and I), induced by laser irradiation (LI) and electron irradiation (EI) are investigated using a first-principles approach, based on the electronic temperature ( T e ) within a two-temperature model (TTM) and by increasing the total number of electrons ( N e ), respectively. Ab initio molecular dynamics (AIMD) simulations provide a clear visualization of how T e and N e induce a structural and electronic transformation process during LI/EI. Our results reveal the diffusion processes of Ag and X ions, the amorphization of the AgX lattices, and a straightforward interpretation of the time evolution for the formation of Ag and X nanoclusters under high values of T e and N e . Overall, the present work provides fine details of the underlying mechanism of LI/EI and promises to be a powerful toolbox for further cross-scale modeling of other semiconductors.

The ab initio molecular dynamics simulations were adopted to study the atomic structures of Co92−xBxTa8 (x = 30, 32.5, 35, 37.5, at%) glassy alloys. The results showed that the local packing of B‐centered clusters was more efficient than that of Co‐ and Ta‐centered clusters. It was also found that B‐centered clusters were the primary structure‐forming clusters. The Kasper polyhedra with a Voronoi index of <0 3 6 0> and <0 2 8 0> are dominant in B‐centered clusters. The <0 3 6 0> clusters could especially be formed into a robust network structure, which plays a key role in the increase of mechanical properties. Such a network structure has a higher activation barrier for structural rearrangement and a larger resistance to plastic flow. Thus, the increase in the fraction of <0 3 6 0> with B content would result in an increase in yield strength, as well as a sharp decrease in compressive plasticity. [ABSTRACT FROM AUTHOR]

By using density functional theory calculations, the initial steps towards Pd metal cluster formation on a pyridine‐terminated self‐assembled monolayer (SAM) consisting of 3‐(4‐(pyridine‐4‐yl)phenyl)propane‐1‐thiol on an Au(1 1 1) surface are investigated. Theoretical modelling allows the investigation of structural details of the SAM surface and the metal/SAM interface at the atomic level, which is essential for elucidating the nature of Pd–SAM and Pd–Pd interactions at the liquid/solid interface and gaining insight into the mechanism of metal nucleation in the initial stage of electrodeposition. The structural flexibility of SAM molecules was studied first and the most stable conformation was identified, planar molecules in a herringbone packing, as the model for Pd adsorption. Two binding sites are found for Pd atoms on the pyridine end group of the SAM. The strong interaction between Pd atoms and pyridines illustrates the importance of SAM functionalisation in the metal nucleation process. Consistent with an energetic driving force of approximately −0.3 eV per Pd atom towards Pd aggregation suggested by static calculations, a spontaneous Pd dimerisation is observed in ab initio molecular dynamic studies of the system. Nudged elastic band calculations suggest a potential route with a low energy barrier of 0.10 eV for the Pd atom diffusion and then dimerisation on top of the SAM layer. [ABSTRACT FROM AUTHOR]

Alanine is used as a transfer standard dosimeter for gamma ray and electron beam calibration. An important factor affecting its dosimetric response is humidity which can lead to errors in absorbed dose calculations. Ab initio molecular dynamics calculations were performed to determine the environmental effects on the electron paramagnetic resonance (EPR) parameters of L‐α‐alanine radicals in acidic and alkaline solutions. A new result, not dissimilar to the closed‐shell amino acid molecule alanine, is that the non‐zwitterionic form of the alanine radical is the stable form in the gas phase while the zwitterionic neutral alanine radical is not a stable structure in the gas phase. Geometric and EPR parameters of radicals in both gas and solution phases are found to be dependent on hydrogen bonding of water molecules with the polar groups and on dynamic solvation. Calculations on the optimized free radicals in the gas phase revealed that for the neutral radical, hydrogen bonding to water molecules drives a decrease in the magnitudes of g‐tensor components gxx and gyy without affecting neither gzz component nor the hyperfine coupling constants (HFCCs). The transfer from the gas to solution phase of the alanine radical anion is accompanied with an increase in the spin density on the carboxylic group's oxygen atoms. However, for the neutral radical, this transfer from gas to solution phase is accompanied with the decrease in the spin density on oxygen atoms. Calculated isotropic HFCCs and g‐tensor of all radicals are in good agreement with experiment in both acidic and alkaline solutions. [ABSTRACT FROM AUTHOR]

The surface chemistry of water on zinc oxides is an important topic in catalysis and photocatalysis. Interaction of D2O with anisotropic ZnO(101‾ 0) surfaces was studied by IR reflection absorption spectroscopy using s‐ and p‐polarized light incident along different directions. Interpretation of the experimental data is aided using isotopologues and DFT calculations. The presence of numerous species is revealed: intact monomers, a mixed 2D D2O/OD adlayer, an anisotropic bilayer, and H‐bonded 3D structures. The isolated water monomers are identified unambiguously at low temperatures. The thermally induced diffusion of water monomers occurs at elevated temperatures, forming dimers that undergo autocatalytic dissociation via proton transfer. Polarization‐ and azimuth‐resolved IR data provide information on the orientation and strength of H‐bonds within the 2D and 3D structures. Ab initio molecular dynamics simulations reveal strong anharmonic couplings within the H‐bond network. [ABSTRACT FROM AUTHOR]

Density functional theory (DFT) was used to study the structure, stability, and bonding in some selected neutral pentaatomic systems, viz., CGa2Ge2, CAlGaGe2, and CSiGa2Ge containing planar tetracoordinate carbon. The systems are kinetically stable, as predicted from the ab initio molecular dynamics simulations. The natural bond orbital (NBO) analysis showed that strong electron donation occurs to the central planar carbon atom by the peripheral atoms in all the studied systems. From the nucleus independent chemical shift (NICS) analysis, it is shown that the systems possess both σ- and π- aromaticity. The presence of 18 valence electrons in these systems, in their neutral form, appears to be important for their stability with planar geometries rather than tetrahedral structures. The nature of bonding is understood through the adaptive natural density partitioning analysis (AdNDP), quantum theory of atoms in molecules (QTAIM) analysis, and also via Wiberg bond index (WBI) and electron localization function (ELF).

In this study, the response of Pu2Zr2O7 and La2Zr2O7 to electronic radiation is simulated, employing an ab initio molecular dynamics method. It is shown that Pu2Zr2O7 undergoes a crystalline-to-amorphous structural transition with 0.3% electronic excitation, while for La2Zr2O7, the structural amorphization occurs with 1.2% electronic excitation. During the microstructural evolution, the anion disorder further drives cation disorder and eventually results in the structural amorphization of Pu2Zr2O7 and La2Zr2O7. The difference in responses to electron radiation between Pu2Zr2O7 and La2Zr2O7 mainly results from the strong correlation effects between Pu 5f electrons and the smaller band gap of Pu2Zr2O7. These results suggest that Pu2Zr2O7 is less resistant to amorphization under local ionization rates that produce a low level of electronic excitation, since the level of the concentration of excited electrons is relatively low in Pu2Zr2O7. The presented results will advance the understanding of the radiation damage effects of zirconate pyrochlores.

The structure and hydrogen adsorption properties of linear HC C-TMH (TM = Sc–Ni) complexes were systematically investigated using a density functional method. The ground states of the HC C-TMH (TM = Sc–Ni) complexes are 2, 3, 4, 3, 4, 3, 2, and 3. The gravimetric H 2 uptake capacities of these ground state HC C-TMH (TM = Sc–Ni) complexes are 4.54–14.56%. Ab initio molecular dynamic simulations indicated that maximal reversible hydrogen storage densities at 77–300 K of the ground state HC C-TMH (TM = Ti–Co) complexes are 6.65–12.00 wt%. The corresponding average adsorption energies are 0.07–0.49 eV. Due to reasonable superior storage capacity and ideal binding energy, HC C-TMH (TM = Ti–Co) complexes are proposed as a suitable hydrogen storage medium at ambient conditions. When HC C-TMH (TM = Ti, V, Cr) are nonground state structures, they can adsorb one more H 2 molecule than their ground states. Unfortunately, the first adsorbed H 2 molecules are dissociated and the adsorption energies are too large. Therefore, the importance of the multiplicity of sorbents for hydrogen storage is emphasized in this work. Image 1 • H 2 storage capacity of HC C-TMH(TM = Sc–Ni) is 4.54–14.56%. • All adsorbed H 2 molecules are in molecular form. • Reversible H 2 storage densities at 77–300 K of HC C-TMH (TM = Ti–Co) are 6.65–12.00%. • Importance of sorbent's multiplicity for H 2 storage study is shown. [ABSTRACT FROM AUTHOR]

Abstract In order to study the effect of the mutual substitution of Fe and Ni on the plasticity of Fe/Ni-based metallic glasses (MGs) from the atomic arrangement structure perspective, we investigate the short-range order (SRO) and medium-range order (MRO) structures of Fe 80 P 14 B 6 , Fe 40 Ni 40 P 14 B 6 and Ni 80 P 14 B 6 MGs using ab initio molecular dynamics (AIMD) simulations method. The results reveal that Fe 40 Ni 40 P 14 B 6 MG has more vertex-sharing clusters and less edge-sharing clusters compared to Fe 80 P 14 B 6 and Ni 80 P 14 B 6 MGs, indicating that Fe 40 Ni 40 P 14 B 6 MG possesses more cavities or boundaries on MRO, which are beneficial for plastic deformation. In addition, large clusters have a relatively strong connection with comparatively smaller clusters in Fe 80 P 14 B 6 and Ni 80 P 14 B 6 MGs while the clusters with the similar size tend to form the nearest neighbor in Fe 40 Ni 40 P 14 B 6 MG. Compared with the former, the connection mode of the latter may form relatively loose packing, which can facilitate plastic deformation. Fe 40 Ni 40 P 14 B 6 MG has larger population of 142×, 1441 and 1661 bond pairs, which are crystal-like clusters, and relatively smaller 1551and 1541. Besides, Fe 40 Ni 40 P 14 B 6 MG has less <0 0 12 0>, <0 1 10 2> and <0 2 10 1> clusters and more <0 4 4 3> and <0 4 4 6> compared to Fe 80 P 14 B 6 and Ni 80 P 14 B 6 MGs, indicating the replacement of Fe by Ni or Ni by Fe in Fe/Ni-based MGs reduces five-fold rotational symmetry, which is beneficial to plasticity. Highlights • The effect of mutual substitution of Fe and Ni on the plasticity of Fe-Ni-P-B metallic glasses (MGs) is studied by AIMD. • As replacing Fe/Ni with Ni/Fe, vertex-sharing clusters increase while edge-sharing clusters decrease, improving plasticity. • Similar sized clusters tend to form nearest neighbor as mutual substituting of Fe and Ni, which is help for plasticity. • The fivefold symmetrical decreases with mutual substituting of Fe and Ni, which is beneficial to plasticity. • Besides the bond nature of elements, the atomic arrangement structure also has a significant role on the plasticity of MGs. [ABSTRACT FROM AUTHOR]

Abstract Zr 3 Fe and Ni-substituted Zr 3 Fe alloys with 30 and 50 at.% Ni were synthesized and their hydrogen absorption/desorption characteristics were compared experimentally (pressure–composition isotherms, thermal desorption spectroscopy, in-situ neutron diffraction) and by computational methods (ab-initio molecular dynamics (AMD), nudged elastic band theory (NEB)). All the alloys absorbed hydrogen to a hydrogen-to-metal atomic ratio of about 1.7, but the hydrides formed were stable at room temperature. The Zr 3 Fe 0.5 Ni 0.5 alloy and its hydrided form were multi-phase. The Zr 3 Fe 0.7 Ni 0.3 alloy was single-phase and retained the C m c m structure of the parent intermetallic. In-situ neutron diffraction with D 2 in place of H 2 showed that the hydride formed in the isotherm measurements, Zr 3 Fe 0.7 Ni 0.3 H 6.88 , had the same structure (C m c m) as Zr 3 FeH 7 , while disproportionation was observed in the hydrogenation of Zr 3 Fe. The kinetics of hydride formation was slower in both the Ni-substituted alloys. Thermal desorption spectroscopy showed that substitution of 0.3Ni significantly destabilized the hydride, lowering the temperature of the principal desorption peak by about 300 K relative to Zr 3 Fe–H 2 , without loss of hydrogen capacity, and avoiding disproportionation. Based on the structures determined by neutron diffraction, AMD and NEB calculations were conducted to compare Zr 3 Fe and Zr 3 Fe 0.7 Ni 0.3 and their hydrides. The AMD calculations predicted that H diffusion was slower in Ni-substituted Zr 3 Fe, in agreement with the experimental observation of slower kinetics, implying a higher activation energy for H migration. The NEB calculations also predicted a higher energy barrier for H migration in Ni-substituted Zr 3 Fe. Highlights • New metal hydride introduced. • Desorption temperature lowered by about 300 °C compared to parent intermetallic. • New alloy and its hydride are single-phase. • Disproportionation noted for Zr 3 FeH 7 is avoided. • Experiment and computational modelling combined to explain improved properties. [ABSTRACT FROM AUTHOR]

Solid, liquid and alloyed phases of gallium play a role in a variety of important technological applications. While many of the gallium phases involved in these applications are metallic, some have been proposed or are known to contain covalently bound Ga dimers. Thus, understanding the nature of bonding in Ga is crucial to the development of Ga-based materials. The solid phase of gallium at ambient conditions, α-Ga, is metallic and composed of molecular dimers, and can serve as a testing ground for studying gallium bonding with electronic structure calculations. We use density functional theory-based molecular dynamics simulations in conjunction with maximally localised Wannier functions to examine the nature of chemical bonding in α-Ga. We propose a geometric criterion for defining various bonding environments, which enables the quantification of covalent and weak bonds in solid gallium. We additionally connect the bonding structure of α-Ga to its phonon density of states and discuss similarities and differences with diatomic halogen crystals. [ABSTRACT FROM AUTHOR]

To gain a deeper understanding of the TiCl4 solvation effects in multi-component ionic liquids, we performed ab initio molecular dynamics simulations of 1-butyl-3-methylimidazolium [C4C1Im]+, tetrafluoroborate [BF4]−, chloride [Cl]− both with and without water and titanium tetrachloride TiCl4. Complex interactions between cations and anions are observed in all investigated systems. By further addition of water and TiCl4 this complex interaction network is extended. Observations of the radial distribution functions and number integrals show that water and TiCl4 not only compete with each other to interact mainly with [Cl]−, which strongly influences the cation-[BF4]− interaction, but also interact with each other, which leads to the fact that in certain systems the cation-anion interaction is enhanced. Further investigations of the Voronoi polyhedra analysis have demonstrated that water has a greater impact on the nanosegregated system than TiCl4 which is also due to the fact of the shear amount of water relative to all other components and its higher mobility compared to TiCl4. Overall, the polar network of the IL mixture collapses by including water and TiCl4. In the case of [Cl]− chloride enters the water continuum, while [BF4]− remains largely unaffected, which deeply affects the interaction of the ionic liquid (IL) network.

GeTe is a fundamental material for phase-change memory, one of the most promising next-generation data storage devices. Doping GeTe with W has achieved both high writing (crystallization) speed at elevated temperature and long data retention (amorphous stability) at room temperature, which overcame a key challenge for phase-change memory. Yet the effect of W on amorphous GeTe remains ambiguous at atomic and electronic scales. By means of ab initio calculations and molecular dynamics (AIMD) simulations, we shed light on this issue and reveal that W would agglomerate during the melt-quench process and the chemically bonded W cluster plays a key role in tuning the overall phase-change performances of GeTe. Furthermore, the strong W-Ge and W-Te bonds show vital impact on the local structure and crystallization of amorphous GeTe as well. The present work provides valuable clues for advancing the understanding of transition metals doping effects on amorphous phase-change materials, and hence promotes the development of novel phase-change alloys with improved information storage performance. [ABSTRACT FROM AUTHOR]

Deep eutectic solvents (DESs) are mixtures of ionic compounds and molecular hydrogen bond donors. Due to the many components and their different interacting subgroups, they give rise to a plethora of many different interactions which can be studied by ab initio molecular dynamics simulations, because within this method all the forces are calculated on the fly and no parametrization prior to the calculation is necessary. Since DESs can be applied in gas capture, for example for SO 2 absorption, we performed ab initio molecular dynamics studies of both the pure choline chloride/glycerol DES and the same mixed with SO 2 . We identified the hydrogen bonding and other specific interactions between all components. With addition of SO 2 , we observed a decrease in the anion-OH group interplay, because the chloride anions form complexes with the SO 2 molecules. Furthermore, the SO 2 molecules are incorporated into the hydrophobic network and the interaction between the hydrogen bonds of all OH groups remain constant. This decrease of anion-OH interaction might be responsible for the more fluid state of the SO 2 -DESs mixture than the pure DES. [ABSTRACT FROM AUTHOR]

The atomic structure, glass forming ability (GFA) and magnetic properties of Co-based (Co 80 P 14 B 6 , Co 80 P 13 C 7 and Co 80 B 14 C 6 ) amorphous alloys were studied by ab initio molecular dynamics simulations. We have analyzed the local atomic structures in the liquid (at 1600 K) and glass state (at 300 K) by pair distribution functions (PDFs), Voronoi Polyhedra (VPs) and bond pair (BPs) analyses. The VPs and PDFs analyses suggest that the GFA of the three Co-based alloys increases in the order of Co 80 B 14 C 6 , Co 80 P 13 C 7 and Co 80 P 14 B 6 . And the BPs analysis uncovers that the three Co-based amorphous structures are mainly composed of perfect and distorted icosahedral BPs such as 1541, 1551 and 1431. We also have calculated the contribution of Co atoms and metalloid elements (B, P, C) to the average magnetic moment of these amorphous alloys based on the density of state (DOS) analysis. [ABSTRACT FROM AUTHOR]

Quantitative analyses of the thermodynamics and kinetics of silicate minerals dissolution at atomic level are difficult currently, both experimentally and computationally. Here, we apply the deep learning, enhancing sampling molecular dynamics and density functional theory to build up a deep neural network potential with quantum mechanics accuracy, which can determine the free energy surfaces, minimum free-energy reaction pathways and kinetic rates for Ca dissolution from the water/dicalcium silicate interface at different temperatures. We find that the Ca dissolution is a spontaneous reaction and follows different minimum free-energy reaction pathways at different temperatures. The dissolution time of the five-coordinated Ca ion is on the order of hundreds of seconds at ambient temperature and increases to the order of nanoseconds after heating. The relatively slow dissolution kinetics comparing to the low free energy barriers of each elementary reaction is attributed to the multi-directional and multi-step nature of the dissolution reaction. This new atomistic insight promotes a better understanding of the dicalcium silicate and cement hydration. [Display omitted] [ABSTRACT FROM AUTHOR]

There has been considerable technological interest in high-entropy alloys (HEAs) since the initial publications on the topic appeared in 2004. However, only several of the alloys investigated are truly single-phase solid solution compositions. These include the FCC alloys CoCrFeNi and CoCrFeMnNi based on 3d transition metals elements and BCC alloys NbMoTaW, NbMoTaVW, and HfNbTaTiZr based on refractory metals. The search for new single-phase HEAs compositions has been hindered by a lack of an effective scientific strategy for alloy design. This report shows that the chemical interactions and atomic diffusivities predicted from ab initio molecular dynamics simulations which are closely related to primary crystallization during solidification can be used to assist in identifying single phase high-entropy solid solution compositions. Further, combining these simulations with phase diagram calculations via the CALPHAD method and inspection of existing phase diagrams is an effective strategy to accelerate the discovery of new single-phase HEAs. This methodology was used to predict new single-phase HEA compositions. These are FCC alloys comprised of CoFeMnNi, CuNiPdPt and CuNiPdPtRh, and HCP alloys of CoOsReRu.

We have investigated the heterogeneous nucleation phenomenon of rare earth metal Yttrium on the surface of alumina. The liquid Y/α-Al 2 O 3 interface was studied at different temperatures and different configured substrates using ab-initio molecular dynamics simulations. The results show that liquid Y atoms near the substrate can form several ordered atomic layers at temperatures slightly above the liquidus of Y, implying occurrence of prenucleation. Although the liquid atoms become slightly less ordered as the temperature rises, the ordered layers are still present. The chemical interaction has a higher impact on the nucleation of metal Y than the temperature, where the oxygen-terminated substrate is more favorable to the nucleation of rare earth Y. The increasing ordered first layer of liquid atoms can promote the following nucleation. We also reveal the effect of the oxide substrate on the heterogeneous nucleation at the liquid-solid interface. The results obtained are useful to deepen our understanding of the behavior of liquid rare earth metal interfaced with α-Al 2 O 3. [ABSTRACT FROM AUTHOR]

The regulating role of graphene coating on improving the electrochemical performance of Li 2 FeP 2 O 7 material are systemically unraveled from the first-principles calculations. [Display omitted] • Graphene coating can significantly improve the poor ionic and electronic conductivityies of Li 2 FeP 2 O 7 material. • The typical parallel and perpendicular Graphene/Li 2 FeP 2 O 7 (0 0 1) and Graphene/Li 2 FeP 2 O 7 (0 1 0) heterostructures exhibit superior thermodynamic and dynamical stabilities. • The conductivities and diffusion coefficients of Li+ ions with the Graphene/Li 2 FeP 2 O 7 heterostructures are effectively enhanced. Pyrophosphate (Li 2 FeP 2 O 7 , LFPO) is proposed as a promising cathode material for Li-ion batteries on account of the high voltage and the two-dimensional lithium ions diffusion channel. Graphene coating could effectively improve the inherent poor ionic and electronic conductivities of Li 2 FeP 2 O 7 material, however, the interfacial interaction and regulating role of the graphene coating on the graphene/Li 2 FeP 2 O 7 (G/LFPO) composite structures are lack of research at the atomic scale. With the aid of first-principles calculations and ab initio molecular dynamics (AIMD) simulations, the interaction mechanism of graphene on the LFPO cathode material has been systematically investigated in terms of the geometrical structure, thermodynamical stability, interfacial charge distribution and electronic property. The analysis of electron localization function (ELF), charge density differences, and density of states strongly suggest the G/LFPO(0 0 1) and G/LFPO(0 1 0) heterostructures exhibit high electrochemical performance. The AIMD simulations show that the parallel and perpendicular G/LFPO(0 0 1) and G/LFPO(0 1 0) heterostructures have high thermodynamical stabilities and electronic conductivities. The diffusion coefficients of Li+ ions in the G/LFPO heterostructures are noticeably enhanced. Our present work would not only provide a fundamental understanding of interfacial interaction and electrochemical properties of G/LFPO composite, but also shed light on the regulating mechanism for the potential phosphate-based cathode material with high electrochemical performance. [ABSTRACT FROM AUTHOR]

[Display omitted] • The effect of atomic structures on GFA was studied by AIMD. • The average degree of LFFS is critical factor for enhancing GFA. • The effect of electronic structures on M s was studied by DFT. The poor glass forming ability (GFA) and magnetic properties of Co-based metallic glasses limit their applications. Herein the effects of similar element substitution of Co by Fe on the GFA and magnetic properties of Co 72.5-x Fe x Si 12.5 B 15 (x = 0, 4.5, 20, and 36) amorphous alloys were studied by experiments and density functional theory (DFT) calculations. The experimental results indicate that Fe substitution for Co improves the GFA of the studied metallic glasses, but in a concentration dependent manner, where Co 52.5 Fe 20 Si 12.5 B 15 shows the best GFA. Meanwhile, the saturated mass magnetization (M s) enhances with increasing Fe content. The atomic structures were analyzed by pair distribution function, coordination number, chemical short-range order, Voronoi polyhedron, and locally five-fold symmetry, and it was found that the highest average degree of the locally five-fold symmetry in Co 52.5 Fe 20 Si 12.5 B 15 is a critical factor for enhancing GFA, which improves the stability of the local atomic structures by increasing the packing density and reducing the potential energy. Density of states and magnetic moments calculated for the four metallic glasses manifest that the larger magnetic moment of Fe atoms and gradual increase in the contribution of the Fe 3d state are responsible for the increase in the M s with Fe content. This work links the GFA and magnetic properties of Co–Fe–Si–B metallic glasses with their atomic/electronic structures, providing reference for designing Co-based metallic glasses with good GFA and enhanced magnetism. [ABSTRACT FROM AUTHOR]

Using ab initio molecular dynamics simulations, we provide direct evidence for the existence of a first-order liquid–liquid phase transition (LLPT) in AsS melt, with a negative Clapeyron slope of the transition line and a critical point around (1323 K < T c < 1423 K, 0.06 GPa < P c < 0.16 GPa). Our predicted transition line is in good agreement with the boundary between high density liquid (HDL) and low density liquid (LDL) suggested in experiment, especially the location of the HDL–LDL–Crystal triple point. Our results show that this first-order LLPT primarily originates from the change of intermediate-range order, i.e., the fourth coordination shell at 4.7 Å and the fifth at 6.7 Å around a S atom in LDL merge into one at 5.4 Å in HDL. Based on our results, a negative thermal expansion coefficient in LDL is predicted. With increasing pressure, the number of 2-fold S-coordinated As atoms decreases in HDL, while that of 3-fold S-coordinated As atoms increases. The total electronic density of states has a deep dip at E F in LDL, which becomes more shallow in HDL. [ABSTRACT FROM AUTHOR]