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The contents of issues 3 and 4 of Structural Chemistry from the calendar year 2015 are summarized in the present review. A brief thermochemical commentary and possible guidelines for future research are added to the summary of each paper. [ABSTRACT FROM AUTHOR]

The contents of issues 1 and 2 for the calendar year 2014 are summarized in the current review of the journal Structural Chemistry. A brief thermochemical commentary is added to the summary of each paper. [ABSTRACT FROM AUTHOR]

Recently following the success of the density functional theory (DFT) in obtaining the structure and thermodynamics of homogeneous and inhomogeneous classical systems such as simple fluids, dipolar fluid and binary hard spheres, this theory was also applied to obtain the density profile of a molecular fluid in between hard planar walls by Kalpaxis and Rickayzen. In the theory of molecular fluids, the direct correlation function (DCF) can be used to calculate the equation of state, free energy, phase transition, elastic constants, etc. It is well known that the hard core molecular models play an important role in understanding complex liquids such as liquid crystals. In this paper, a classical fluid of nonspherical molecules is studied. The required homogeneous (DCF) is obtained by solving Orenstein-Zernike (OZ) integral equation numerically. Some of the molecules in the liquid crystals have a sphere shape and this kind of molecular fluid is considered here. The DCF sphere of the molecular fluid is calculated and it will be shown that the results are in good agreement with the pervious works and the results of computer simulation. Finally the electro-optical properties of ellipsoid liquid crystal using DCF of these molecules are calculated. [ABSTRACT FROM AUTHOR]

In this paper, we study the structural, electronic, magnetic, mechanical and thermal properties of Half-Heusler CoMnTe, using the Density Functional Theory (DFT) with the generalized gradient approximation (GGA) and GGA plus the Hubbard correction (GGA+U). The obtained results show that the compound is more stable in γ -phase with the ferromagnetic (FM) configuration than the nonmagnetic (NM) among the three considered structural phases (α , β , γ) and there is no possibility of martensitic transformation under the tetragonal distortion effect. The computed total magnetic moments of CoMnTe by GGA and GGA+U are 4 μ B and 4.13 μ B , respectively, arising mainly from the Mn atom. The obtained density of states and band structures using GGA approach show that the compound exhibits half-metallic behavior with 100% spin polarization. As the Hubbard is added, the electronic properties show an electronic phase transition from half-metallic to metallic behavior with 68% spin polarization. While the thermal and mechanical properties show very small changes, confirming that the studied compound is mechanically and dynamically stable. • CoMnTe compound is more stable in γ -phase with the ferromagnetic configuration. • CoMnTe compound is mechanically and thermodynamically stable. • CoMnTe compound is promising for spintronic applications. [ABSTRACT FROM AUTHOR]

The use of a sacrificial cathode additive that contains a large amount of lithium is one potential solution to compensate for the irreversible capacity loss associated with next‐generation anodes such as silicon. Antifluorite‐type Li6CoO4 has attracted attention as a potential cathode additive owing to its remarkably high theoretical lithium extraction capacity. However, the complex mechanism of lithium extraction as well as the oxygen loss from Li6CoO4 is not well understood. A generalizable computational thermodynamics and experimental framework is presented to understand the lithium‐extraction pathway of Li6CoO4. It is found that one lithium per formula unit can be topotactically extracted from Li6CoO4, followed by an irreversible and nontopotactic phase transformation to Li2CoO3 or LiCoO2 depending on the temperature. The results show that peroxide species may form to charge‐compensate for Li extraction which is undesirable as this can lead to gas release during battery operation. It is suggested that charging Li6CoO4 at an elevated temperature that the electrolyte can withstand, redirects the reaction pathway and prevents the formation of intermediate peroxide species making it an effective and stable sacrificial cathode additive. [ABSTRACT FROM AUTHOR]

The energies and stresses associated with the decohesion of β-SiC in the presence of mobile Pd and Ag impurities are studied from first principles. Density functional theory calculations are parameterized with a generalized cohesive zone model and are analyzed within a thermodynamic framework that accounts for realistic boundary conditions in the presence of mobile impurities. We find that Pd impurities will embrittle SiC when Pd is in equilibrium with metallic Pd precipitates. Our thermodynamic analysis predicts that Pd embrittles SiC by substantially reducing the maximum stress of decohesion as a result of a phase transition between decohering planes involving an influx of Pd atoms. The methods presented in this work can be applied to study the thermodynamics of decohesion of SiC in other aggressive environments containing oxygen and water, for example, and yield environment dependent cohesive zone models for use in continuum approaches to study crack propagation and fracture. [ABSTRACT FROM AUTHOR]

Surfaces and interfaces of ferroelectric oxides exhibit enhanced functionality, and therefore serve as a platform for novel nano and quantum technologies. Experimental and theoretical challenges associated with examining the subtle electro‐chemo‐mechanical balance at metal‐oxide surfaces have hindered the understanding and control of their structure and behavior. Here, combined are advanced electron‐microscopy and first‐principles thermodynamics methods to reveal the atomic‐scale chemical and crystallographic structure of the surface of the seminal ferroelectric BaTiO3. It is shown that the surface is composed of a native <2 nm thick TiOx rock‐salt layer in epitaxial registry with the BaTiO3. Using electron‐beam irradiation, artificial TiOx sites with sub‐nanometer resolution are successfully patterned, by inducing Ba escape. Therefore, this work offers electro‐chemo‐mechanical insights into ferroelectric surface behavior in addition to a method for scalable high‐resolution beam‐induced chemical lithography for selectively driving surface phase transitions, and thereby functionalizing metal‐oxide surfaces. [ABSTRACT FROM AUTHOR]

The structural and elastic properties of ZnSe with B3 and B1 phases under different pressure have been investigated by the first principle method based on density functional theory. The obtained structural parameters of ZnSe in both B3 and B1 structures are in good agreement with the available values. The transition pressure of ZnSe from B3 to B1 was predicted as 14.85 GPa by using the enthalpy–pressure data, which is well in line with experimental result. According to the obtained elastic constants, the elastic properties such as bulk modulus, shear modulus, Young's modulus, ductile/brittle behavior and elastic anisotropy as a function of pressure for polycrystalline of ZnSe are discussed in details. In the frame work of quasi-harmonic Debye model, the temperature and pressure dependencies of the Debye temperature and heat capacity of ZnSe are obtained and discussed in the wide ranges. [ABSTRACT FROM AUTHOR]

Many technological applications such as heat treatment processes and their computational modeling and simulation require knowledge of the thermodynamic properties of the phases involved. Depending on the alloy system, experimental methods to obtain high-accuracy values especially for specific heat capacity of ultra-high-melting alloys will require high-temperature equipment, which is expensive and restricted in terms of the maximum temperature. We present a method for obtaining these values from first-principles (density functional theory) calculations and compare this method to experimental data of Mo-based alloys. The ab initio approach is based on the computation of elastic properties, which are then used to fit a Birch-Murnaghan equation of state to solve the Debye model. Experimental values are obtained by differential scanning calorimetry of single-phase and three-phase samples, from which individual phase properties are reconstructed using a phase mixing approach. It can be concluded that all methods employed agree within reasonable limits of accuracy, showing the validity of the first-principles approach. [ABSTRACT FROM AUTHOR]

Theoretical investigation on TbTe for its structural, electronic, magnetic, and thermodynamic stuffs has been carried within density functional theory (DFT) as implemented in WIEN2K code. TbTe was found stable in ferromagnetic phase. The calculated ground-state parameters were found in a good agreement with the experimental data. The compound was found to have a structural stability in cubic B1 (NaCl-type structure) phase, but under the application of high pressure (at 27 GPa), it undergone to B2 (CsCl-type structure) phase of pressure. The second-order elastic constants and mechanical properties like Young’s modulus, Shear modulus, Poisson ratio, Cauchy pressure (C12-C44), and Pugh’s ratio (B/G) were calculated. The present calculations confirmed the ductile nature of TbTe. Further, the thermodynamic investigations have been carried using quasi-harmonic Debye approximation. We have calculated the pressure and temperature dependence of Debye temperature (휃D), bulk modulus (B), thermal expansion (α), heat capacities (CV), and entropy (S) in the temperature range of 0 to 1000 K and pressure range of 0 to 25 GPa. [ABSTRACT FROM AUTHOR]

The plane-wave pseudo-potential method, which is based on density functional theory, is used to determine the structure, elastic constants and phase transition properties of transition metal nitride (TMN; TM = Ti, Zr, Hf, V, Nb and Ta) nanocomposite films under external pressures. Enthalpy–pressure and volume–energy relations of TMNs with different structures are calculated, and their relative stability is discussed. Mechanical stability of external pressure is calculated, and changes in elastic constants with external pressure are analyzed. The present study obtains influence of external pressure on the mechanical properties of material. By analyzing total energy–volume relation, enthalpy–pressure relation and mechanical stability, phase transition law of TMNs under external pressure is obtained. [ABSTRACT FROM AUTHOR]

Using dynamical density functional theory and Brownian dynamics simulations, we investigate the influence of a driven tracer particle on the density distribution of a colloidal suspension at a thermodynamic state point close to the liquid side of the binodal. In bulk systems, we find that a localised region of the colloid-poor phase, a ‘cavitation bubble’, forms behind the moving tracer. The extent of the cavitation bubble is investigated as a function of both the size and velocity of the tracer. The addition of a confining boundary enables us to investigate the interaction between the local phase instability at the substrate and that at the particle surface. When both the substrate and tracer interact repulsively with the colloids we observe the formation of a colloid-poor bridge between the substrate and the tracer. When a shear flow is applied parallel to the substrate the bridge becomes distorted and, at sufficiently high shear-rates, disconnects from the substrate to form a cavitation bubble. [ABSTRACT FROM PUBLISHER]

The structural, electronic, elastic and thermodynamic properties of Curium Monopnictides Cm X ( X = N, P, As, Sb and Bi) are investigated using first-principles calculations based on the density functional theory (DFT) and full potential linearized augmented plane wave (FP-LAPW) method under ambient condition and high pressure. The exchange-correlation term is treated using two approximations spin-polarized local density approximation (LSDA) and spin-polarized generalized gradient approximation generalized (GGA). The structural parameters such as the equilibrium lattice parameters, bulk modulus and the total energies are calculated in two phases: namely NaCl (B1) and CsCl (B2). The obtained results are compared with the previous theoretical and experimental results. A structural phase transition from B1 phase to B2 phase for Curium pnictides has been obtained. The highest transition pressure is 122 GPa for CmN and the lowest one is 10.0 GPa for CmBi compound. The electronic properties show that these materials exhibit half-metallic behavior in both phases. The magnetic moment is found to be around 7.0 B. The mechanical properties of Cm X ( X = N, P, As, Sb and Bi) are predicted from the calculated elastic constants. Our calculated results are in good agreement with the theoretical results in literature. The effect of pressure and temperature on the thermodynamic properties like the cell volume, bulk modulus and the specific heats C and C, the entropy and the Grüneisen parameter have been foreseen at expanded pressure and temperature ranges. [ABSTRACT FROM AUTHOR]

The present study deals with first-principles calculations of the thermal properties of ZnTe in the two phases namely, zinc-blende and wurtzite. The calculations are mainly performed using the density functional theory with the local density approximation and response-function calculations. The full phonon dispersions throughout the Brillouin zone are presented. The temperature dependence of the lattice parameters, bulk modulus, entropy and heat capacity are examined and discussed. Our findings agree reasonably well with those available in the literature. [ABSTRACT FROM AUTHOR]

A theoretical investigation on structural, dynamical, phase diagram and thermodynamic properties of beryllium telluride (BeTe) under high pressure and temperature is presented in the framework of density functional theory. The calculated structural parameters of BeTe in both zinc blende (ZB) and nickel arsenide (NiAs) structures are in reasonable agreement with available experimental data and previous theoretical work. The phonon dispersion relations, dielectric tensor and Born effective charge are investigated within the density functional perturbation theory (DFPT). The investigation of the phase diagram indicated that the NiAs structure BeTe becomes stable at high pressure and temperature. Based on the quasiharmonic Debye model, the pressure and temperature dependences of bulk modulus, Grüneisen parameter, Debye temperature, specific heat and thermal expansion coefficient are all successfully obtained. We hope that the theoretical results reported here can give more insight into the structural and thermodynamic properties of other semiconductors at high temperature and pressure. [ABSTRACT FROM AUTHOR]