Predicted structures and superconductivity of LiYHn (n = 5–10) under high pressure†
The structures of LiYHn (n = 5–10) compounds in the pressure range of 0–300 GPa have been extensively explored using the CALYPSO structure prediction method based on the particle swarm optimization algorithm and first-principles calculation. Four stable structures (P21/m LiYH6, C2/c LiYH8, P LiYH9, Rm LiYH10) and three metastable phases (Pnma LiYH6, P LiYH8, Immm LiYH9) were predicted. They all exhibit metallic and superconducting behavior in their respective stable pressure ranges, and the predicted superconducting transition temperature Tc is within 22–109 K when the pressure is greater than 100 GPa. It was found that after doping Li into YHn (n = 6, 9, 10), the H2 units in the system increased, the electron–phonon coupling interaction weakened, and Tc decreased when the structural characteristics, electronic density of states distribution, and superconductivity of LiYHn and YHn (n = 6, 8, 9, 10) were compared. Systems that have a high density of H_s states and a low number of Y_d states at the Fermi level have stronger electron–phonon coupling (EPC) interactions and higher Tc.