Phase transitions and equation of state of zirconium under high pressure
Simone Anzellini, François Bottin, J. Bouchet, Agnès Dewaele
Abstract
X-ray diffraction measurements performed in a diamond anvil cell under quasihydrostatic conditions up to 142 GPa at 300 K evidence an $\ensuremath{\alpha}$-Zr $\ensuremath{\rightarrow}$ (17 GPa) $\ensuremath{\omega}$-Zr $\ensuremath{\rightarrow}$ (35 GPa) $\ensuremath{\beta}$-Zr phase transitions sequence. Ab initio molecular dynamics calculations performed on the body-centered cubic $\ensuremath{\beta}$-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 $\ensuremath{\beta}$-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 $\ensuremath{\beta}$-Zr.