As titanium is a highly utilized metal for structural light-weighting, its phases, transformation pathways (transition states), and structures have scientific and industrial importance. Impurities, pressure, and temperature control the phase stability and transition barriers in most industrial and geophysical materials - in Ti, interstitial O, N, or C retard while substitutional Al and V suppress the ω phase. Using a proper solid-state nudged elastic band (SS-NEB) method employing double-climbing images (C2-NEB) combined with density-function theory (DFT+U) methods for accurate energetics, we detail the pressure-induced α (ductile) to ω (brittle) transformation at the coexistence pressure. We find two transition states along the minimal-enthalpy path (MEP) and discover a metastable body-centered orthorhombic (bco) structure, with stable phonons, a lower density than the endpoint phases, and decreasing stability with increasing pressure.
@article{arxiv.1510.04358,
title = {Titanium $\alpha - \omega$ phase transformation pathway and a predicted metastable structure},
author = {N. A. Zarkevich and D. D. Johnson},
journal= {arXiv preprint arXiv:1510.04358},
year = {2017}
}