Stable structures and superconductivity of Ca-As-H system under high pressure

Obtaining room-temperature superconductors has always been a research hotspot in the field of condensed matter physics. Previous studies have shown that doping strategies can effectively enhance the superconducting properties of materials. In this work, we utilized the first-principles and particle swarm optimization methods to search for the structures of the Ca-doped As-H ternary system, and calculated the electronic and superconducting properties of new structures. Two thermodynamically stable hydrides have been identified under high pressure. The P 4/ nmm -Ca 2 AsH 4 phase remains thermodynamically stable in the pressure range of 90 -200 GPa, and the Cc -Ca 2 AsH 6 phase exhibits stability over a broader range of 79-200 GPa. Electron-phonon coupling analysis indicates that the superconducting critical temperatures ( T c ) of P 4/ nmm -Ca 2 AsH 4 and Cc -Ca 2 AsH 6 are 11 and 16 K at 100 GPa. The incorporation of Ca notably lowers the thermodynamic stability pressure of As-H compounds with higher hydrogen stoichiometry, thereby improving their synthesis accessibility.