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

Abstract

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.