High-temperature and high-pressure physical properties of CuI with zinc-blende phase by a systematic ab initio investigation

A systematic ab initio investigation has been performed to determine the elastic stability, the structural and finite-temperature thermodynamic properties of copper iodide (CuI) in the zinc-blende phase under pressure. All calculations are carried out based on the pseudopotential density functional method, in which we employ the generalized gradient approximation of the revised Perdew-Burke-Ernzerhof form and local density approximation of Ceperly and Adler parameterized by Perdew and Zunger together with plane-wave basis sets for expanding the periodic electron density. The obtained normalized volume dependence of the pressure and the equation-of-state parameters including equilibrium volume, isothermal bulk modulus and its pressure derivatives are in excellent agreement with the experimental data and other theoretical results. The elastic constants are calculated and the investigation of the mechanical stability from the elastic constants under pressure indicates that the zinc-blende CuI is stable up to 10 GPa. Through the careful evaluation with the quasi-harmonic Debye model in which the phononic effects are considered, a complete set of thermodynamic data up to 800 K, including the bulk modulus, volume thermal expansion coefficient, heat capacity, entropy, Debye temperature, and Grüneisen parameter of CuI with zinc-blende structure is achieved. This set of data is considered as the useful information to understand the high-temperature and high-pressure properties of CuI.