中国有色金属学报(英文版)
Transactions of Nonferrous Metals Society of China
| Vol. 33 No. 10 October 2023 |
（1. Institute of Nuclear Physics and Chemistry, China Academy of Engineering Physics, Mianyang 621900, China;
2. School of Materials Science and Engineering, Central South University, Changsha 410083, China;
3. State Key Laboratory of Powder Metallurgy, Central South University, Changsha 410083, China）
Abstract:Various phases of TiHx (x=1-2) were constructed, with all possible H-atom configurations being considered. The first-principles energetics calculations were performed to evaluate their formation preference and mechanical and thermodynamic stabilities. All the results were then combined to construct the stable and metastable phase stability diagrams of TiHx. It is suggested that many stable and metastable TiHx phases have very comparable formation energies and thus are likely to co-exist. Their relative stabilities are strongly depended on temperature (T) and the partial pressure of hydrogen (p(H2)). Over the entire T and p(H2) range of interest, γ-TiH and γ-TiH2 are the only two stable phases. ε-TiH, γ-TiH1.5, ε- and δ-TiH1.75, and ε-TiH2 can possibly present as metastable phases. These metastable phases are all mechanically stable, and have a thermodynamic tendency to continuously absorb or release H until reaching the equilibrium phases of γ-TiH2 or γ-TiH.
Key words: titanium hydride; phase stability; metastable phase; first-principles
