Structural stabilities, elastic and thermodynamic properties of Scandium Chalcogenides via first-principles calculations

The high-pressure structural (B1–B2) phase transition and the elastic properties of ScS and ScSe are studied using the full-potential augmented plane wave plus local orbitals method (FP-APW + LO) with the generalized-gradient approximation (GGA) exchange-correlation functional. The elastic constants and their pressure dependence are calculated following the total energy variation with strain technique. The stability and the ductility mechanisms for these compounds are discussed via the electronic density of states (DOS) and the elastic constants Cij. The thermodynamic properties of (B1) structure are predicted through the quasi-harmonic Debye model, in which the lattice vibrations are taken into account. The variation of bulk moduli, the thermal expansion coefficient, the heat capacities and the Debye temperature with pressure and temperature are successfully obtained. To our knowledge this is the first quantitative theoretical prediction of the elastic, high pressure and thermal properties for the investigated compounds and still awaits experimental confirmations.