Titanium metal at high pressure: Synchrotron experiments and ab initio calculations

The high pressure behavior of titanium metal is investigated experimentally using angle dispersive synchrotron x-ray diffraction as well as theoretically using ab initio electronic structure methods. Our calculations predict a direct ω to bcc transformation around 80 GPa without any intermediate crystal phases. The ${\beta }^{\prime }$ (bcc-structure) Ti phase was experimentally observed to coexist with the ω phase at pressures between 40 and 80 GPa on compression at ambient temperature. High-temperature treatment at 80 GPa results in a formation of a new η phase with a monoclinically distorted bcc structure. On decompression the η phase transforms to the pure ${\beta }^{\prime }$ phase.