Structural and thermodynamic properties of SbAsGa2 and SbPGa2 chalcopyrites

The structural and elastic behaviour of the chalcopyrite SbPGa2 and SbAsGa2 crystals has been determined by means of first principles calculations using the full-potential augmented plane wave (FPLAPW) method. Ground state properties such as the lattice parameters (a, c and u), bulk modulus B, its pressure derivative B′, have been directly calculated and compared to previous experimental and theoretical results when available. We have determined the elastic parameters (C11, C12, C33, C44 and C66), which have not been calculated and measured yet. Thermal properties, including the linear and cubic expansion coefficients and the heat capacity, have been estimated using a quasi-harmonic Debye model. To our knowledge this is the first quantitative theoretical prediction of elastic and thermal properties for these compounds and still awaits experimental confirmations.