Mechanical properties, thermal conductivity, and optical properties of a novel layered compound Bi3O2S2Cl under pressure

The structure stability, mechanical properties, thermal conductivity, and optical properties of a novel layered tetragonal compound Bi3O2S2Cl have been investigated at pressure up to 25 GPa by using first-principles calculations based on density functional theory in this work. The lattice parameters of Bi3O2S2Cl calculated by Perdew–Burke–Ernzerhof functional in the ground state agree well with the experimental results. Moreover, the calculated phonon dispersion curves and elastic constants Cij suggest that Bi3O2S2Cl is mechanically and dynamically stable from 0 to 25 GPa. The bulk modulus B and the shear modulus G calculated from Cij at different pressures demonstrate that the ductility of Bi3O2S2Cl is increased by external pressure. Furthermore, the influence of pressure on longitudinal sound velocity vl, transverse sound velocity vt, aggregate acoustic velocities vm, Debye temperature ΘD, Poisson’s ratio σ, and Grüneisen parameter γ are systematically studied. Meanwhile, the elastic anisotropy index AU and the shear anisotropy factors A1, A2, and A3 are also investigated, together with the directional linear compressibility and Young’s modulus under pressure from 0 to 25 GPa. The results show that the anisotropy of Bi3O2S2Cl increases under external pressure. Afterward, we further evaluated the minimum thermal conductivity of Bi3O2S2Cl under pressure by using both Clark’s model and Cahill’s model. At ambient pressure, it exhibits a relatively low thermal conductivity of 0.365 Wm−1 K−1. Although the minimum thermal conductivity increases with the increase of pressure, it remains a potential thermal barrier coating material in extreme environments. Finally, the calculations of the optical properties of Bi3O2S2Cl under different pressures show that this new layered tetragonal compound is a promising energy harvesting and optoelectrical material in extreme environments. Graphical abstract