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Abstract: Because of the significance of the first and second pressure derivatives of the isothermal bulk modulus, a detailed theoretical study of the high-pressure rocksalt phase of ZnO under high pressure and temperature has been carried out by means of first-principles density functional theory calculations combined with the quasi-harmonic Debye model in which the phononic effects are considered. Particular attention is paid to the predictions of the isothermal bulk modulus and its pressure derivatives which play central role in the formulation of approximate equations of state for the first time. [Copyright &y& Elsevier]

Abstract: A detailed theoretical study of the isothermal and adiabatic bulk moduli of MgF2 with a fluorite structure under high pressure and temperature has been carried out by means of first-principles density functional theory calculations combined with the quasi-harmonic Debye model in which the phononic effects are considered. Particular attention is paid to the prediction of the isothermal bulk modulus and its first and second pressure derivatives for the first time. The calculated ground state properties agree well with other theoretical values. At extended pressure and temperature ranges, the variation of the bulk modulus which plays a central role in the formulation of approximate equations of state has also been predicted. The properties of MgF2 with a fluorite structure are summarized in the pressure range of 0–135 GPa and the temperature up to melting temperature 1500 K. [Copyright &y& Elsevier]

Abstract: Molecular dynamics simulations have been performed to investigate the thermal expansivity of MgO at high temperature using the very similar Lewis–Catlow and Stoneham–Sangster shell model potentials. In order to take account of non-central forces in crystals, the breathing shell model is also introduced in simulation. The volume thermal-expansion coefficient α P of MgO dependence of the temperature T at 0 and 135GPa have been obtained and compared with the available experimental and theoretical results. Compared with shell model potentials, the molecular dynamics results obtained using breathing shell model potentials are more compressible. At an extended pressure and temperature ranges, α P has also been predicted. [Copyright &y& Elsevier]

Abstract: The constant temperature and pressure molecular dynamics (MD) have been performed to investigate the isothermal bulk modulus of MgO under high pressures and temperatures, using the shell model (SM) potential functions consisted of the Coulomb, dispersion, and repulsion interactions. In order to take account of non-central forces in crystals, the breathing shell model (BSM) is also introduced in MD simulation, in which the repulsive radii of oxygen ions are allowed to deform isotropically under the effects of other ions in the crystal, with each core and breathing shell being linked by a harmonic spring with force constant k. The isothermal bulk modulus K T of MgO dependence of the compression ratio V/V 0 and the pressure P have been obtained from MD runs at T =300 and 2000K, and compared with the available theoretical results. Compared with SM potential of Stoneham and Sangster [Phil. Mag. B 52 (1985) 717], the MD results with potential of Lewis and Catlow (LC) [J. Phys. C 18 (1985) 1149] are found to be in good agreement with the studies based on ab initio calculations, and the results obtained using BSM potential are more compressible. Meanwhile, K T dependence of temperature T at zero pressure is investigated. At an extended pressure and temperature ranges, K T has also been predicted. The properties of MgO are summarized in the pressure 0–200GPa ranges and the temperature up to 3500K. [Copyright &y& Elsevier]

Abstract: The pressure–volume–temperature (P–V–T) equation of state (EOS), isothermal bulk modulus, and thermal expansivity of CaF2 with cubic fluorite-type structure are investigated using the constant temperature and pressure shell model molecular dynamics (MD) method with effective pair potentials which consist of the Coulomb, dispersion, and repulsion interaction. It was shown that MD simulation is very successful in accurately reproducing the measured volumes of the CaF2 over a wide range of pressures. The simulated P–V data matched X-ray diffraction experimental results up to 9.5GPa at 300K. In addition, volume thermal-expansion coefficient and isothermal bulk modulus were also calculated and compared with available experimental data and the latest theoretical results at ambient condition. At extended temperature and pressure ranges, The P–V EOS under different isotherms at selected temperatures, T–V EOS under different isobars at selected pressures, thermal expansivity, and isothermal bulk modulus were predicted up to 1500K and 10GPa. The detailed knowledge of thermodynamic behavior and EOS at extreme conditions are of fundamental importance to the understanding of the physical properties of CaF2. [Copyright &y& Elsevier]

Abstract: Shell model molecular dynamics (MD) method is used to predict the structure and thermodynamic properties of MgO at high temperatures and high pressures using the Stoneham–Sangster and Lewis–Catlow potentials, respectively. In order to account for the observed large departures from the Cauchy relation of the elastic constants of the MgO, the breathing shell model (BSM) is also introduced in MD simulation, in which the repulsive radii of oxygen ions are allowed to deform isotropically under the effects of other ions in the crystal. The properties including the expansivity, constant-pressure heat capacity, isothermal bulk modulus are calculated in a wide range of temperatures (300–3000K) and pressures (0–150GPa). The obtained structural and thermodynamic parameters are compared with the available experimental data and other theoretical results. Compared with Stoneham–Sangster and Lewis–Catlow potentials, the MD simulation with BSM is very successful in reproducing accurately the measured volumes of MgO and the results are more compressible. Meanwhile, some thermodynamic parameters have been predicted at elevated temperatures and high pressures. The detailed knowledge of thermodynamic behavior of the major Earth-forming mineral—periclase (MgO) at extreme P–T conditions are of fundamental importance to our understanding of the Earth''s lower mantle and the history of the Earth''s formation. [Copyright &y& Elsevier]

Abstract: Molecular dynamics (MD) simulations have been performed to investigate the pressure–volume–temperature (P–V–T) relationship of MgO under high pressures and temperatures using the very similar shell model (SM) potentials with those of Stoneham and Sangster (SS) [Philos. Mag. B 52 (1985) 717] and Lewis and Catlow (LC) [J. Phys. C 18 (1985) 1149]. In order to take account of non-central forces in crystals, the breathing shell model (BSM) is also introduced in MD simulation, in which the repulsive radii of oxygen ions are allowed to deform isotropically under the effects of other ions in the crystal, with each core and breathing shell being linked by a harmonic spring with force constant k. The lattice parameter a, thermoelastic parameter αK T, and P–V relationship under different isotherms at selected temperatures and T–V relationship at zero pressure, have been obtained and compared with the available experimental data and other theoretical results. Compared with SM-SS and SM-LC potentials, the MD simulation with BSM is very successful in reproducing accurately the measured volumes of MgO. At an extended pressure and temperature ranges, P–V–T relationship has also been predicted. The properties of MgO are summarized in the pressure range of 0–2000kbar and the temperature up to 5000K. [Copyright &y& Elsevier]

Abstract: The heat capacities at constant pressure and constant volume, and thermal expansivity are calculated for ZnO with rocksalt-type and zinc-blende-type cubic structures over a wide range of temperatures using molecular dynamics simulations with interactions due to effective pair-wise potentials which consist of the Coulomb, dispersion, and repulsion interaction. It is shown that the calculated structural and thermodynamic parameters including lattice constant, thermal-expansion coefficient, isothermal bulk modulus and its pressure derivative at ambient condition are in good agreement with the available experimental data and the latest theoretical results. At extended pressure and temperature ranges, lattice constant and heat capacity have also been predicted. The structural and thermodynamic properties of ZnO with cubic structure are summarized in the 300–1500 K temperature ranges and up to 100 kbar pressure. [Copyright &y& Elsevier]