Transformation of Optical Anisotropy Origins in Perovskite-Related Materials: A First-Principles Study

Perovskite-related compounds are of vital significance in the optical element and laser industry and other fields. Exploring the contributions of microscopic units that form the perovskite framework is one efficient way to design new materials with targeted performance. In this work, we acquired the linear and nonlinear optical properties and analyzed the superior functional units in determining optical anisotropy and second harmonic generation (SHG) of typical perovskite-related compounds from inorganic to organic, namely, BaTiO3, Sr2MgMoO6, CsPbI3, CH3NH3PbI3, ClOK3, and B6O10ClK3. The results indicate that distorted octahedral units are dominant in optical anisotropy for the vast majority of perovskite-related compounds. For instance, [TiO6], [Mo-6], [Pb(I)6], and [OK6] octahedral units are decisive birefringence origins to BaTiO3, Sr2MgMoO6, CsPbI3 and CH3NH3PbI3, and ClOK3, respectively, most of which contribute over 90%. When it comes to B6O10ClK3, it is A-site [B6O10] groups but not [ClK6] octahedral units that lead the optical anisotropy, as the A-site groups present stronger covalency than octahedral units. In addition, through SHG-density analysis, A-site [B6O10] groups are also dominant SHG origins, which means A-site ionic groups are possible linear and nonlinear optical origins in this case.