Phase Transitions And Equation Of State Of Zirconium Under High Pressure

X-ray diffraction measurements performed in a diamond anvil cell under quasihydrostatic conditions up to 142 GPa at 300 K evidence an alpha-Zr -> (17 GPa) omega-Zr -> (35 GPa) beta-Zr phase transitions sequence. Ab initio molecular dynamics calculations performed on the body-centered cubic beta-Zr at 300 and 1000 K and between 0 and 100 GPa produced an equation of state in excellent agreement with the experiments. The stability of beta-Zr under pressure has been verified by numerical heating-quenching experiments, and the anharmonicity of the thermal vibrations has been evaluated. No dynamical instability due to a soft mode is evidenced between 25 and 100 GPa, in line with the experimental finding of a wide stability range for beta-Zr.