Abstract
The high pressure-temperature behavior of titanium has been studied with x-ray diffraction in resistively heated and laser-heated diamond anvil cells up to 200 GPa and K. The stability fields of , and have been determined in this range. and , which had been evidenced earlier under nonhydrostatic compression, are also observed in helium pressure transmitting medium. Equation-of-state parameters are proposed for and at 300 K, and at high temperature. The stability fields of the , and phases are also studied using the projector-augmented wave method based on density-functional theory. Using the relevant core radius to avoid overlapping between atomic spheres, and relaxing cells and atomic positions, we show that all those phases have a stability domain at 0 K. We explain why and were calculated to be unstable in earlier works. In addition, a new phase, called -Ti, which is a distortion of , is predicted to form between 80 and 120 GPa and below K.
4 More- Received 13 October 2014
- Revised 3 February 2015
DOI:https://doi.org/10.1103/PhysRevB.91.134108
©2015 American Physical Society