Prediction of high-<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msub><mml:mi>T</mml:mi><mml:mi>c</mml:mi></mml:msub></mml:math> superconductivity in ternary lanthanum borohydrides
Xiaowei Liang, Aitor Bergara, Xudong Wei, Xiaoxu Song, Linyan Wang, Rongxin Sun, Hanyu Liu, Russell J. Hemley, Lin Wang, Guoying Gao, Yongjun Tian
Abstract
The study of superconductivity in compressed hydrides is of great interest due to measurements of high critical temperatures $({T}_{c})$ in the vicinity of room temperature, beginning with the observations of ${\mathrm{LaH}}_{10}$ at 170--190 GPa. However, the pressures required for synthesis of these high-${T}_{c}$ superconducting hydrides currently remain extremely high. Here we show the investigation of crystal structures and superconductivity in the La-B-H system under pressure with particle-swarm intelligence structure-searches methods in combination with first-principles calculations. Structures with seven stoichiometries, LaBH, ${\mathrm{LaBH}}_{4}, {\mathrm{LaBH}}_{6}, {\mathrm{LaBH}}_{7}, {\mathrm{LaBH}}_{8}$, La(${\mathrm{BH})}_{3}$, and $\mathrm{La}{({\mathrm{BH}}_{4})}_{3}$ were predicted to become stable under pressure. Remarkably, the hydrogen atoms in ${\mathrm{LaBH}}_{8}$ were found to bond with B atoms in a manner that is similar to that in ${\mathrm{H}}_{3}\mathrm{S}$. Lattice dynamics calculations indicate that ${\mathrm{LaBH}}_{7}$ and ${\mathrm{LaBH}}_{8}$ become dynamically stable at pressures as low as 109 and 48 GPa, respectively. Moreover, the two phases were predicted to be superconducting with a critical temperature ${T}_{c}$ of 93 K and 156 K at 110 GPa and 55 GPa, respectively (${\ensuremath{\mu}}^{*}$ = 0.1). The present results provide guidance for future experiments targeting hydride superconductors with both low synthesis pressures and high ${T}_{c}$.