Titanium metal at high pressure: Synchrotron experiments andab initiocalculations

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 β^' (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 β^' phase.