Investigation of structural, electronic, and thermoelectric properties of K2Hg2Se3 and K2Hg2Te3 compounds from first principles

Increasing energy efficiency has been the subject of many studies and thermoelectricity has become an important option in increasing energy efficiency. Thermoelectric is the science that examines the transformation of electric and heat energy. Thermoelectric materials are used in cooling and waste heat power generation applications. The performance of a thermoelectric material is determined by the dimensionless thermoelectric value (ZT), which requires a high Seebeck coefficient ($ S $), high electrical conductivity ($ \sigma $), and low thermal conductivity ($ \kappa $). In this study based on density functional theory; structural, electronic and thermoelectric properties of K$_2$Hg$_2$Se$_3$ and K$_2$Hg$_2$Te$_3$ materials are investigated. Equilibrium lattice constants, bulk modulus, electronic band structures, partial and total state density of states were obtained by generalized gradient approach. Thermoelectric coefficients are calculated by solving the semi-classical Boltzmann transport equation. The Seebeck coefficients in both materials are found to be larger in p-type doping than the n-type doping. ZT values in both materials are larger in p-type doping to than n-type doping. ZT values obtained in p-type doping are larger for K$_2$Hg$_2$Te$_3$ compared to K$_2$Hg$_2$Se$_3$. In this study, we showed that K$_2$Hg$_2$Te$_3$ with p-type doping has a value of ZT=1.49 at the operational temperature of 500 K, which is a promising thermoelectric material candidate. Keywords: Ab initio calculations, density functional theory, thermoelectric properties 2019,57 pages