Abstract
The structural, electronic, optical, elastic, and thermoelectric (TE) characteristics of Na2YCuX6 (X = Br, Cl) halide double-perovskites (HDPs) were investigated by using first principle approach within WIEN2K code. Perdew, Burke and Ernzerhof generalized-gradient approximation (PBEsol-GGA) with modified Becke-Johnson (mBJ) potential were used in the current investigations. Enthalpy of formation energies (E-f) determined for Na2YCuBr6 and Na2YCuCl6 were -2.29 and -1.955 eV, correspondingly which verify the stability of both compounds. Na2YCuBr6 is discovered to be semiconducting with indirect bandgap (E-g) of 2.492 and Na2YCuCl6 has direct E-g of 2.571 eV. Absorption coefficient shows largest values at 5.74 and 6.92 eV for Na2YCuBr6 and Na2YCuCl6, correspondingly, which lie in UV range. Pugh's ratio (B/G) values were calculated as 2.00 and 4.62 for Na2YCuCl6 and Na2YCuBr6, correspondingly which ensure the ionic bond and ductile characteristics of the compounds. From the TE calculations, ZT shows maximum values of 0.74 and 0.73 for Na2YCuBr6 and Na2YCuCl6, respectively. Results showed that investigated materials are efficient candidates for optoelectronic and TE appliances.