Optoelectronic, thermoelectric, and elastic properties of Cu₆PSe₅X (X = Br, I) argyrodites using density functional theory

Abstract Cu 6 PSe 5 X (X = Br, I) argyrodites’ structural, optoelectronic, elastic, anisotropic, and thermal properties are examined using the method of ab initio through the density functional theory. There is a significant match found between the calculated ground state structural characteristics and the available data. Based on the Birch-Murnaghan fit curve for optimization, it is found that both compounds achieve ground state. The energy bandgap of Cu 6 PSe 5 Br is 0.606 eV (indirect), while Cu 6 PSe 5 I has a band gap of 0.697 eV (direct) according to the mBJ-functional. They appear to be promising prospects for high frequency applications since the UV area contains the most notable absorption peak. The BoltzTrap package, which is incorporated into WIEN2K, has been used to determine the thermoelectric properties. Cu 6 PSe 5 Br thermal conductivity reaches a maximum of 4.6 × 10 14 ( W/mKs ) when the temperature rises to 1000 K, whereas Cu 6 PSe 5 I has a maximum value of 5.24 × 10 14 ( W/mKs ). At room temperature, the ZT values for Cu 6 PSe 5 Br and Cu 6 PSe 5 I are 0.803 and 0.972, respectively. The elastic constants show that the materials are mechanically stable. The estimated Poisson ratio, which ranges from 0.264 for the Br-based to 0.252 for the I-based, indicates that bonding has a significant ionic character. Compared to Cu 6 PSe 5 I, Cu 6 PSe 5 Br has a greater melting temperature. Since these materials have appropriate energy bandgaps, they can be used in several optoelectronic devices.