Structure and superconductivity in compressed Li-Si-H compounds: Density functional theory calculations

作者：Peiyu Zhang, Ying Sun, Xue Li, Jian Lv, Hanyu Liu · 发表于：Physical review. B./Physical review. B · 年份：2020 · DOI：10.1103/physrevb.102.184103 · 被引用次数：43 · 研究领域：Hydrogen Storage and Materials、High-pressure geophysics and materials、Superconductivity in MgB2 and Alloys

Previous experimental evidence showed that silane ($\mathrm{Si}{\mathrm{H}}_{4}$) becomes a superconductive phase at a critical temperature (${T}_{\mathrm{c}}$) of 17 K above 96 GPa, although this observation was not supported by later experiments due to the fact that $\mathrm{Si}{\mathrm{H}}_{4}$ was measured to decompose into amorphous silicon and solid hydrogen at $\ensuremath{\sim}60--90\phantom{\rule{0.16em}{0ex}}\mathrm{GPa}$ and then recrystallized into a nonmetallic phase up to $\ensuremath{\sim}130\phantom{\rule{0.16em}{0ex}}\mathrm{GPa}$. Given lithium has a short atomic radius and low electronegativity, it could be incorporated into the binary hydrides and act as an electron donor by doping electrons into the lattice of parent binary hydrides, enabling the modification of crystal structures and superconductivity for the resulting ternary hydride system. In this work, therefore, we attempted to chemically tune crystal structures and improve the superconductivity of the Si-H system via lithium incorporation, by performing structure searching simulations on the Li-Si-H system at a wide pressure range of 50--350 GPa. As a result, four stable stoichiometries of $\mathrm{LiSi}{\mathrm{H}}_{5}, \mathrm{LiSi}{\mathrm{H}}_{6}, \mathrm{LiS}{\mathrm{i}}_{2}{\mathrm{H}}_{9}$, and $\mathrm{L}{\mathrm{i}}_{2}\mathrm{Si}{\mathrm{H}}_{6}$, as well as two metastable stoichiometries of $\mathrm{LiSi}{\mathrm{H}}_{4}$ and $\mathrm{LiSi}{\mathrm{H}}_{8}$, were uncovered under high pre...