First principles studies of elastic and thermodynamic properties of fcc-VH2 with pressure and temperature

In this work, we study elastic and thermodynamic properties of VH2 at different pressures and temperatures. Elastic constants and bulk modulus of VH2 decrease with increase in temperature, and hence increase with pressure. Thermal expansion of the crystal lattice will be suppressed by high pressure. When the temperature is 1500 K, 15.99 GPa of pressure can completely restrain the volume expansion caused by temperature. At a given pressure, the lower the temperature, the easier the cell compression. At low temperatures, Cv is proportional to T3, and Cv tends to the Dulong–Petit limit at higher temperatures. The Debye temperature increases with pressure, but decreases with temperature. At low temperature and low pressure, thermal expansion coefficient increases sharply with temperature. At high temperature and high pressure, the increasing trend slows down.

Research Highlights
► The First-principle and quasi-harmonic Debye model are employed to investigate VH2 at different pressures and temperatures.
► Elastic constants (C11, C12, and C44) and bulk modulus B decrease with temperature and increase with pressure, respectively.
► At 1500 K, just 15.99 GPa of pressure can restrain the volume expansion caused by temperature.
► We also studied thermal properties such as Cv and α of VH2.We found that like most solid materials, at low temperatures, Cv is proportional to T3 and that Cv tends to the Dulong–Petit limit at higher temperatures. The Debye temperature increases with pressure, but decreases with temperature. At low temperature, α increases, and with temperature increasing tendency becomes small at high temperature. Higher the pressure smaller the thermal expansion.