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

Obtaining room-temperature superconductors has long 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 employed first-principles calculations combined with the particle swarm optimization method to explore the structural possibilities of the Ca-doped As–H ternary system and to calculate the electronic and superconducting properties of the newly identified structures. Two thermodynamically stable hydrides were found under high pressure. The P4/nmm-Ca₂AsH₄ phase remains thermodynamically stable within the pressure range of 90–200 GPa, while the Cc-Ca₂AsH₆ phase exhibits stability over a broader range of 79–200 GPa. Electron-phonon coupling analysis indicates that the superconducting critical temperatures (T_c) of P4/nmm-Ca₂AsH₄ and Cc-Ca₂AsH₆ are 11 K and 16 K at 100 GPa, respectively. The incorporation of Ca significantly reduces the thermodynamic stability pressure of As–H compounds with higher hydrogen content, thereby improving their synthetic accessibility.