Structural, electronic and thermoelectric properties of LiAlX2 (X=S and Se) chalcopyrites: promising for thermoelectric power generators

Herein, we have inquired the structural, electronic and thermoelectric properties of the couple of chalcopyrite structured solids LiAlX2 (X=S and Se) with the help of density functional theory (DFT), which is tracked by resolution of the Boltzmann transport equation with the constant relaxation time calculations. The LDA (Localized Density Approximation), PBE (Perdew-Burke-Ernzerhof), PBEsol (PBE functional revised for solids) and WC (Wu-Cohen) exchange correlation potentials have been used. The calculated lattice constants a = 5.271 angstrom; c = 10.178 angstrom and a = 6.226 angstrom; c = 12.165 angstrom for LiAlS2 and LiAlSe2 respectively and the band gap of the mentioned compounds are found in range from 1.74 eV to 3.13 eV. The dependency of thermoelectric parameters are calculated with different temperature (300-800K) and carrier concentration 10(18) 10(19) cm(-3). From the study of ZT (figure of merit's ZT= S-2 sigma T/kappa the dimensionless parameter) and it is found that it's value for both the compounds in n-type as well as in p-type region is 'unity'. Since these compounds can be the promising candidate for thermoelectric devices also these compounds are non-toxic, eco-friendly and good alternative for the green and renewable source of electric power generators.