High-pressure phases of titanium: First-principles calculations

We investigate through first-principles calculations the controversial observation of the high-pressure orthorhombic (γ and δ) phases of titanium. Our calculations predict the transition sequence ω-γ-β under pressure, and reveal that the δ phase is elastically unstable under isotropic compression. We attribute its observation to nonhydrostatic stresses present in the diamond-anvil cell experiments. We find the γ phase to be stable in the 102--1120.3em0exGPa pressure range, with the upper limit of this pressure range increasing under nonhydrostatic conditions.