First-principles investigations on elastic and thermodynamic properties of zirconium under pressure

The structural, elastic and thermodynamic properties of α, ω and β Zr under pressure have been investigated using first-principles calculations. The axial ratio c/a increases with pressure for α Zr, while it keeps nearly constant for ω Zr. The pressure dependence of elastic constants are presented covering bulk modulus, shear modulus, Young’s modulus, Poisson’s ratio, aggregate sound velocities and elastic anisotropy. The mechanical stability and ductility/brittleness are also assessed. Comparing the two hexagonal structures at zero temperature, it is found that ω Zr is more incompressible with higher elastic modulus, higher aggregate sound velocities and lower elastic anisotropy. The thermal properties including the normalized volume, bulk modulus, heat capacity, Debye temperature and volume thermal expansion coefficient in a wide range of pressure and temperature for three phases of Zr are predicted for the first time, and a remarkable consistency with experimental results are demonstrated.