Structural, electronic, thermoelectric, and optical properties of anti-perovskite X3SiO (X = Ba, Sr, Ca) using the first principle method

Abstract

Anti-perovskite materials have unique structural and electronic properties that offer significant potential for thermoelectric and optical applications, mainly because of their direct gap semiconducting behavior. In this work, we investigate the structural, electronic, thermoelectric, and optical properties of anti-perovskite X₃SiO (X = Ba, Sr, Ca) using the density functional theory (DFT) method. These properties were computed by employing the generalized gradient approximation with the Perdew-Burke-Ernzerhof (GGA-PBE) exchange-correlation function. The structural, electronic, and optical properties were calculated using the CASTEP code, while thermoelectric properties were calculated using the BoltzTraP code that utilized the Boltzmann transport equation (BTE). Our analysis of band structure for Ba₃SiO, Sr₃SiO, and Ca₃SiO shows that these materials have direct band gaps with semiconducting behavior at
Γ-Γ k-points. The band gap values are 0.44 eV, 0.43 eV, and 0.11 eV for Ba₃SiO, Sr₃SiO, and Ca₃SiO respectively. The elastic property analysis indicates that all three compounds are brittle due to their Pugh’s ratio ≦ 0.5. Furthermore, the thermoelectric analysis revealed that Ba₃SiO and Sr₃SiO compounds are n-type materials, while the Ca₃SiO compound is a p-type material at 300 K. However, our results show that anti-perovskite X₃SiO (X = Ba, Sr, Ca) exhibits relatively poor thermoelectric performance with low figure of merit (ZT) values of 9.66  10^–4, 9.59  10^–4, and 2.50  10^–2 for Ba₃SiO, Sr₃SiO, and Ca₃SiO, respectively, at room temperature. Regarding optical properties, these compounds have a wide absorption spectrum from 0 eV to 30 eV, from the infrared to the ultraviolet region. The maximum peaks in reflection coefficient were observed in the high ultraviolet light energy range (>20 eV), suggesting that Ba₃SiO, Sr₃SiO, and Ca₃SiO are excellent reflectors.