Stable structures and superconducting properties of Ca-La-H compounds under pressure

The calcium hydrides and lanthanum hydrides under high pressures have been reported to have good superconducting properties with high-T_C. In this work, the structures and superconductivities of Ca-La-H ternary hydrides have been studied by genetic algorithm and density functional theory calculations. Our results show that at the pressure range of 100-300 GPa, the most stable structure of CaLaH₁₂has aCmmmsymmetry, in which there is a H₂₄hydrogen cage. It can be expected to have high possibility to be synthesized due to its large stability. Furthermore, the predictedT_Cof theCmmm-CaLaH₁₂structure is about 140 K at 150 GPa, and when the pressure decreases to 30 GPa, the CaLaH₁₂structure with aC2/msymmetry has a predictedT_Cof about 49 K. The CaLaH₁₂is suggested to be a stable good superconductor with large stability and performs well at relatively low pressures.