Pressure-stabilized electride Li10Si with superconducting and superionic behavior

Electrides have attracted increasing interest due to their diversely physical properties, including low work function, high catalytic activity, as well as potential superconductivity. In this work, using first-principles crystal structure prediction method in combination with first-principles calculations, we uncovered seven thermodynamically stable electrides in the electron-rich Li-Si system at a pressure range of 25--100 GPa, namely $C2/c\phantom{\rule{4pt}{0ex}}{\mathrm{Li}}_{5}\mathrm{Si}, Cmcm\phantom{\rule{4pt}{0ex}}{\mathrm{Li}}_{6}\mathrm{Si}, P{2}_{1}/m\phantom{\rule{4pt}{0ex}}{\mathrm{Li}}_{7}\mathrm{Si}, Imma\phantom{\rule{4pt}{0ex}}{\mathrm{Li}}_{7}\mathrm{Si}, C2/c\phantom{\rule{4pt}{0ex}}{\mathrm{Li}}_{8}\mathrm{Si}, Cmcm\phantom{\rule{4pt}{0ex}}{\mathrm{Li}}_{9}\mathrm{Si}$, and $I222\phantom{\rule{4pt}{0ex}}{\mathrm{Li}}_{10}\mathrm{Si}$. Among these predicted structures, five of them are superconductor. In particular, the superconducting critical temperature ${T}_{\text{c}}$ of $I222\phantom{\rule{4pt}{0ex}}{\mathrm{Li}}_{10}\mathrm{Si}$ was estimated to be approximately 15 K at 95 GPa. Our in-depth analysis shows that this high superconductivity is attributed to the strong coupling between the Li-$p$ electrons and the Li-dominated phonon softening at low frequencies. Additionally, ${\mathrm{Li}}_{10}\mathrm{Si}$ undergoes a phase transition from solid state to superionic state at 60 GPa and 850 K, where Si atoms remain fixed to form the lattice, allowing for the diffusion of Li atoms within the interstitial position. Our results reveal the emergence of two distinct dynamic states of superconducting and superionic in this particular system, and the further experimental studies are thus stimulated.