Novel structures and superconductivities of calcium-lithium alloys at high pressures: A first-principles study

Exposing a material to high pressures can fundamentally influence its crystal and electronic structure, leading to the formation of new materials with unique physical and chemical properties. Here, we have conducted a systematic search for Ca-Li alloys by using a global minima search based on particle-swarm optimization algorithm in combination with density functional theory calculations. We predict that Calcium and Lithium with a high Ca composition CaLi, Ca2Li and Ca3Li exist, and a strikingly decomposition-combination-decomposition oscillating behavior with pressure is revealed. All predicted Ca-Li compounds are metallic and good electron-phonon superconductors with transition temperatures (Tc) of around 8-19 K. The superconductivity mainly originates from the low-energy Ca vibrations and the pressure dependence of Tc is dominated by the phonon softening/hardening.