Discovery of Electron-Neutral Electrides with Pressure-Induced Superconductivity

Electrides have been largely restricted to electron-rich compositions, leaving the applications of electron-neutral electrides scarcely explored and poorly understood. Here we report the discovery of an electron-neutral ternary electride, LiAlGe, which undergoes an unusual pressure-driven evolution: a semiconducting, nonelectride F4̅3m-LiAlGe phase at ambient conditions transforms into metallic electride phases, F4̅3m- (6.4-13.7 GPa) and Cmmm-LiAlGe phase (13.7-40.0 GPa). First-principles calculations further predict superconductivity in both high-pressure phases. To extend this concept, we combined high-throughput computation with machine learning (ML) to identify ten additional electron-neutral electrides adopting the LiAlGe-type topology. ML analysis reveals that the cooperative interplay between distinct cation species and their atomic radii is a key descriptor governing electride formation in ternary neutral systems. We synthesized LiAlGe and experimentally verified its high-pressure behavior. Synchrotron X-ray measurements confirmed the predicted F4̅3m to Cmmm transition at 14.3 GPa, in excellent agreement with the calculated 13.7 GPa. Importantly, both high-pressure phases were found to be superconducting under appropriate pressures, validating the theoretical predictions and establishing electron-neutral electrides as a previously overlooked class of superconducting materials.