Atomic structure, mechanical quality, and thermodynamic property of TiHx phases

Titanium hydrides TiHx (x = 1, 1.25, 1.5, 1.75, and 2) with the cubic fluorite-type (face-centered cubic, delta phase) and face-centered-tetragonal (epsilon phase, c/a < 1; gamma phase, c/a > 1) structures were systematically investigated and compared through first-principles calculation. The H location of TiHx was carefully determined by comparing the calculated properties with experimental results. Moreover, the mechanical properties of epsilon and gamma phases were calculated and found to play an important role in the brittle/ductile behavior of TiHx phases. In addition, the thermodynamic quantities were also derived for providing a deeper understanding of TiHx phases. The calculated results were widely compared with the available experimental results in the literature, and could clarify the three controversies regarding atomic configuration, stability, and hydrogen embrittlement of TiHx phases in the literature. (C) 2013 AIP Publishing LLC.