Pressure induced impact on mechanical, electrical, optical, and thermal properties of Li4OX2 (X = Cl, Br and I): DFT study

We investigate the pressure effect on Li4OX2 (X = Cl, Br, and I) for the first time using DFT simulation. Li4OCl2 shows mechanical stability up to 8 GPa, whereas Li4OBr2 has stability up to 30 GPa pressure according to the Born stability criteria. In contrast, Li4Ol2 becomes unstable above 3.0 GPa pressure. Hence, anomalies were observed for Li4OX2 (X = Cl, Br, and I) solid electrolyte for elastic parameters, Cij under pressure study. The elastic moduli are isotropic in the xy plane, conversely, along the xz and yz plane anisotropic behavior is observed. There is a band gap that exists at zero temperature and pressure. The contribution at the fermi level mainly comes from the O 2p states. The highest reflectivity (∼98 %) was observed for Li4OCl2 at ∼ 17 eV in the IR-visible-UV region showing that this material under study may be considered as a potential coating material to avoid solar heating. The smaller value of the volume thermal expansion coefficient for Li4OCl2 indicates stronger atomic bonding exists, which was also observed from the elastic parameter analysis.