Theoretical investigation of the structural, electronic and thermodynamic properties of cubic and orthorhombic XZrS_3 (X = Ba,Sr,Ca) compounds

摘要

The structural, electronic and thermodynamic properties of XZrS3 (X=Ba,Sr,Ca) compounds with orthorhombic Pbnm and cubic Pm-3m phases have been investigated and reported. The calculations have been performed using various density functionals within the generalized gradient approximation. The obtained lattice parameters for the Pnma phase reveal very good agreement with experiment. The computed electronic band structures show that in the cubic phase the material of interest is an indirect band-gap (R-?) semiconductor, whereas it is a direct band gap (?-?) in the orthorhombic phase. The semiconducting XZrS3 (X=Ba,Sr,Ca) compounds are found to satisfy the stability criteria against volume change. Based on the quasi-harmonic Debye model, the thermodynamic properties of the material in question have been predicted taking into account the lattice vibrations. The variation of the lattice constant, bulk modulus, heat capacity, Debye temperature and thermal expansion coefficient as a function of pressure in the range 0-30 GPa and temperatures of 0-1500K has been computed. Our findings show that external effects such as temperature and pressure are highly effective in tuning some of the macroscopic properties of the compounds under study.