Novel Superconducting Electrides in Ca–S System under High Pressures
Yun-Xian Liu, Chao Wang, Shuai Han, Xin Chen, Hairui Sun, Xiaobing Liu
Abstract
Due to their unique structure properties, most of the electrides that possess extra electrons locating in interstitial regions as anions are insulators. Metallic and superconducting electrides are very rare under ambient conditions. We systematically search possible compounds in Ca–S systems stabilized under various pressures up to 200 GPa, and investigate their crystal structures and properties using first-principles calculations. We predict a series of novel stoichiometries in Ca–S systems as potential superconductors, including P 2 1 / m Ca 3 S, P 4mbm Ca 3 S, Pnma Ca 2 S, Cmcm Ca 2 S, Fddd CaS 2 , Immm CaS 3 and C 2/ c CaS 4 . The P 4 mbm Ca 3 S phase exhibits a maximum T c value of ∼20 K. It is interesting to notice that the P 2 1 / m Ca 3 S and Pnma Ca 2 S stabilized at 60 and 50 GPa behave as superconducting electrides with critical temperatures T c of 7.04 K and 0.26 K, respectively. More importantly, our results demonstrate that P 2 1 / m Ca 3 S and Pnma Ca 2 S are dynamically stable at 5 GPa and 0 GPa, respectively, indicating a high possibility to be quenched to ambient condition or synthesized using the large volume press.