First principles comparative studies of thermoelectric and other properties in the cubic and hexagonal structure of CsCdCl3 halide perovskites

Abstract

We present First-principles studies of cubic and hexagonal structured CsCdCl3, using Norm Conserving (PBE-NC) and Projected Augmented Wave (PBE-PAW) pseudopotentials. From our results, the hexagonal structure has direct bandgaps of 2.54 eV and 2.24 eV, within the PBE-PAW and PBE-NC pseudopotentials respectively. Whereas, the cubic structure possess bandgaps of 1.76 eV and 1.58 eV for PBE-PAW and PBE-NC pseudopotentials respectively. Also, from the elastic properties calculations, the results revealed higher values of Vicker's hardness, elastic constants C11 and C12, Young, Bulk and Shear moduli in the cubic structure than the hexagonal structure with the exemption in Pugh's ratio having a higher value in hexagonal structure. Further analysis of the calculated elastic properties reveals that CsCdCl3 is ductile and satisfied the conditions for elastic stability. Across calculated temperature range, the PBE-PAW pseudopotentials give higher electrical and thermal conductivity per relaxation time in the two structures, with a nearly linear increase in cubic and hexagonal structures. From 0 K up to the room temperature, the thermal conductivity per relaxation time in both pseudopotentials and crystal structures converged to the same values, while above 300 K the cubic phase has higher thermal conductivity per relaxation time. The hexagonal structure has a higher figure of merit with a significant peak located at 50 K with PBE-PAW and PBE-NC pseudopotential method. The work revealed that CsCdCl3 possess interesting thermoelectric properties and will be applicable as thermoelectric material.