Structural, energetic and elastic properties of Cu2ZnSn(SxSe1-x)4 (x=1, 0.75, 0.5, 0.25, 0) alloys from first-principles computations

We have computed the structural, energetic and elastic properties of the Cu2ZnSn(SxSe1-x)(4) (x = 1, 0.75, 0.5, 0.25, 0) alloys using ab initio density functional theory. For alloys containing both S and Se, a careful choice of permutations of positions for S and Se has to be made for accurately finding the minimum energy structure. The computed lattice constants increase as the fraction of S atoms in the unit cell decreases. However, the internal parameters did not show much variation with alloy composition. The computed elastic constants show that all alloys are mechanically stable. All the elastic constants and moduli, except C-16, increase in magnitude while Poisson's ratio stays the same as the S content of the alloys increases. The computed magnitudes of elastic constant C-16 were found to be two orders of magnitude lower compared to the other elastic constants. (C) 2014 Elsevier Ltd. All rights reserved.