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The pressure-induced structural phase transition of rhenium monocarbon (ReC) is investigated via the projector augmented wave (PAW) method with the generalized gradient approximation (GGA). Using the first-principles calculations, the equilibrium structural parameters of ReC in rocksalt (NaCl), cesium chloride (CsCl), zinc blende (ZB), wurtzite (WZ), nickel arsenide (NiAs) and tungsten carbide (WC) types are successfully obtained, and the results are well consistent with other theoretical data. It is firstly noted that WC-ReC translates into CsCl-ReC at 510.50 GPa by analyzing the enthalpy difference versus pressure. From the calculated elastic constants, the aggregate elastic modulus ( B , G , E ), the Poisson's ratio ( σ ) and the Debye temperature Θ D of WC-type are also derived. It is observed that all the data of WC-ReC obtained increase monotonically with increasing pressure. Meanwhile, the thermodynamic properties of WC-ReC under high temperature and high pressure are investigated applying nonempirical Debye model in the quasi-harmonic approximation.

The structural phase transition and elastic properties of zirconium nitride (ZrN) are investigated by using density functional theory (DFT) methods within the Perdew–Burke–Ernzerhof (PBE) form of generalized gradient approximation (GGA). Our calculated equilibrium structural parameters of ZrN are in good agreement with the available experimental data and other theoretical results. The obtained phase transition B1 → B2 at ca. 210.41 GPa. This conclusion is in agreement with that of Hao et al., contrary to the theoretical calculation of Ojha et al. using a two-body interionic potential theory. We also found that the NiAs and WC phases are not stable in the whole pressure range considered. Especially, the elastic properties of B1-ZrN under high pressure are predicted. It is noted that the elastic constants, bulk moduli, shear moduli, compressional and shear wave velocities as well as Debye temperature of B1-ZrN increase monotonically with increasing pressure. By analyzing G/B, the brittle-ductile behavior of ZrN is assessed. In addition, polycrystalline elastic properties are also obtained successfully for a complete description of elastic properties.

The structural phase transition and elastic properties of monoclinic, orthoI and orthoII zirconium dioxide (ZrO2) are investigated by using pseudopotential plane-wave methods within the Perdew–Burke–Ernzerhof (PBE) form of generalized gradient approximation (GGA). Our calculated equilibrium structural parameters of ZrO2 are in good agreement with the available experimental data. On the basis of enthalpy versus pressure data obtained from our theoretical calculations for high pressure, we find that phase transition pressure from monoclinic to orthoI and orthoI to orthoII are ca. 7.94 GPa and 11.58 GPa, respectively, which are in good agreement with the experimental observations. Especially, the elastic properties of orthoII ZrO2 under high pressure are studied for the first time. We note that the elastic constants, bulk moduli, shear moduli, compressional and shear wave velocities as well as Debye temperature of orthoII ZrO2 increase monotonically with increasing pressure. By analyzing G/B, the brittle-ductile behavior of ZrO2 is assessed. In addition, polycrystalline elastic properties are also obtained successfully for a complete description of elastic properties.

We present a study of the structural phase transition and elastic properties of titanium (Ti) by using the projector augmented wave (PAW) within the Perdew–Burke–Ernzerhof (PBE) form of generalized-gradient approximation (GGA). The calculated phase transition ω → γ at ca. 116.5 GPa, which agrees well with the experimentally observed transition pressure of 116.0 ± 4.0 GPa. However, other theoretical calculations are far from experimental value. We also find that the δ phase is not stable in the whole pressure range considered and phase transition from γ to β phase occurs at 162.4 GPa. This conclusion is in accordance with those of Joshi et al. and Vermal et al., but in disagreement with the experimental results of Vohra et al. and Akahama et al. Especially, the elastic properties of ω -Ti under high pressure are studied for the first time. We note that the compressional and shear wave velocities as well as the bulk B and shear moduli G increase monotonically with increasing pressure. By analyzing R G / B , the brittle–ductile behavior of Ti is assessed. Polycrystalline elastic properties are also obtained successfully for a complete description of elastic properties.