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arXiv · 1911.09293

High-Temperature Superconductivity in the Ti--H System at High Pressures

Jin Zhang·Jeffrey M. McMahon·Artem R. Oganov·Xinfeng Li·Xiao Dong·Huafeng Dong·Shengnan Wang
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Abstract

Search for stable high-pressure compounds in the Ti--H system reveals the existence of titanium hydrides with new stoichiometries, including Ibam-Ti$_2$H$_5$, I4/m-Ti$_5$H$_{13}$, I$\bar{4}$-Ti$_5$H$_{14}$, Fddd-TiH$_4$, Immm-Ti$_2$H$_{13}$, P$\bar{1}$-TiH$_{12}$, and C2/m-TiH$_{22}$. Our calculations predict I4/mmm $\rightarrow$ R$\bar{3}$m and I4/mmm $\rightarrow$ Cmma transitions in TiH and TiH$_2$, respectively. Phonons and the electron--phonon coupling of all searched titanium hydrides are analyzed at high pressure. It is found that Immm-Ti$_2$H$_{13}$ rather than the highest hydrogen content C2/m-TiH$_{22}$, exhibits the highest superconducting critical temperature T$_{c}$. The estimated T$_{c}$ of Immm-Ti$_2$H$_{13}$ and C2/m-TiH$_{22}$ are respectively 127.4--149.4 K ($\mu^{*}$=0.1-0.15) at 350 GPa and 91.3--110.2 K at 250 GPa by numerically solving the Eliashberg equations. One of the effects of pressure on T$_{c}$ can be attributed to the softening and hardening of phonons with increasing pressure.

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Jin Zhang, Jeffrey M. McMahon, Artem R. Oganov, Xinfeng Li, Xiao Dong, Huafeng Dong, Shengnan Wang. 2019-11-21. High-Temperature Superconductivity in the Ti--H System at High Pressures. https://doi.org/10.1103/physrevb.101.134108

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