Predicted superconductivity in one-dimensional A3Hf2B3-type electrides

Abstract

Inorganic electrides are considered potential superconductors due to the unique properties of their anionic electrons. However, most electrides require external high-pressure conditions to exhibit considerable superconducting transition temperatures (T_c). Therefore, searching for superconducting electrides under low or moderate external pressures is of significant research interest and importance. In this work, a series of A₃Hf₂B₃-type compounds (A = Mg, Ca, Sr, Ba; B = Si, Ge, Sn, Pb) were constructed and systematically studied based on density functional theory calculations. According to the analysis of the electronic structures and phonon dispersion spectrums, stable one-dimensional electrides Ca₃Hf₂Ge₃, Ca₃Hf₂Sn₃, and Sr₃Hf₂Pb₃, were screened out. Interestingly, the superconductivity of these electrides were predicted from electron phonon coupling calculations. It is highlighted that Sr₃Hf₂Pb₃ showed the highest T_c, reaching 4.02 K, while the T_c values of Ca₃Hf₂Ge₃ and Ca₃Hf₂Sn₃ were 1.16 K and 1.04 K, respectively. Moreover, the T_c value of Ca₃Hf₂Ge₃ can be increased to 1.96 K under 20 GPa due to the effect of phonon softening. This work enriches the types of superconducting electrides and has important guiding significance for the research on constructing electrides and related superconducting materials.