Electronic Anisotropy and Superconductivity in One-Dimensional Electride Ca₃Si

Inorganic electrides have gained remarkable attention for their intrinsic physical properties derived from loosely bound anionic electrons. Herein, using ab initio evolutionary structure search, we found that the formulation of Ca and Si with the stoichiometric ratio of 3:1 can be stabilized under mildly external pressure, where the hexagonal P6₃/mmc phase is the most stable structure under a wide pressure range from 13.5 to 104 GPa. Based on the analysis of the electrostatic difference potential as an identifier of electrides, together with the electronic structure and electron localization function results, we have identified the P6₃/mmc Ca₃Si as the one-dimensional (1D) electride, whose chemical formula could be expressed as [Ca₃Si]²⁺:2e^-. Interestingly, the electron mobility and the electron-phonon interaction strength of P6₃/mmc Ca₃Si electride present the strong electronic anisotropy, illustrating the 1D electron confinement nature. Moreover, due to the strong electron-phonon coupling between interstitial electrons and phonons from Ca atoms, the P6₃/mmc Ca₃Si exhibits superconductivity with a predicted superconducting transition temperature T_c of about 17.6 K at 100 GPa, which is the highest among the already known 1D electrides. Our works provide new insight into new thermodynamically stable related alkaline earth based electrides and their potential for high performance in electronics and catalytic applications.