Characterization of vibrational and mechanical properties of quaternary compounds Cu2ZnSnS4 and Cu2ZnSnSe4 in kesterite and stannite structures

In this paper, structural, elastic, and dynamical properties of Cu2ZnSnS4 and Cu2ZnSnSe4 are calculated for kesterite and stannite structures using the density functional and density functional perturbation theories. The stability of these two materials, either in a kesterite or stannite crystal structure, is verified by using both elastic constants and phonon dispersions results. No significant difference is observed between the calculated energetic, mechanical, and dynamical properties of the kesterite and stannite phases of either compound. Using extensively rich sampled first Brillouin-zone phonon data, relaxation time-dependent lattice thermal conductivities are predicted through the solution of the phonon Boltzmann transport equation. For both compounds, the relaxation time-dependent lattice thermal conductivity of the stannite structure along the x or y directions is found to be similar to 25% larger than its value in the z direction; in contrast, the predicted difference in the kesterite structure is only similar to 5%.NSFNational Science Foundation (NSF) [DMR 0844082]; AFRLUnited States Department of DefenseUS Air Force Research Laboratory; Scientific and Technological Research Council of TurkeyTurkiye Bilimsel ve Teknolojik Arastirma Kurumu (TUBITAK) [TUBITAK-BIDEB-2219]We would like to acknowledge the support from NSF (DMR 0844082) to the International Institute of Materials for Energy Conversion at Texas A&M University as well as AFRL. We would also like to thank for generous time allocation made for this project by the Supercomputing Center of Texas A&M University. One of us (T. G.) would like to thank The Scientific and Technological Research Council of Turkey TUBITAK-BIDEB-2219 program for support