Thermo-elastic and bonding features of the CdMgS2 crystal: an ab initio study

An investigation of the chalcopyrite and rock-salt phase of the CdMgS2 compound was carried out in terms of FP-LAPW calculations. We found that the electron density of crystals contains important information required for studying the phase transition in this compound. By means of the atoms-in-molecules (AIM) and electron localization function (ELF) formalisms, we found that the chalcopyrite semiconductor phase of the investigated compound undergoes a phase transition to a metallic rock salt. The closure of the band gap is reflected in an increasing electronic delocalization across a change in the nature of the bonding. Thermal effects were included via a quasi-harmonic non-empirical Debye model in order to study their linear expansion parameters. Calculations of the elastic constants of this crystal are possible in both phases, but, obviously, this does not imply that the rock-salt phase is the thermodynamically stable one for this crystal.