Md. Zahidur Rahaman

Highlighted with improved long-term thermal and environmental stability, all-inorganic metal halide perovskites exhibit tunable physical properties, cost-effective synthesis, and satisfactory optoelectronic performance, attracting increasing research interest worldwide. However, a less explored feature of these materials is their strong spin–orbit coupling (SOC), which is the hidden force influencing not only band structure but also properties including magnetoresistance, spin lifetime, and singlet-triplet splitting. This review provides an overview of the fundamental aspects and the latest progress of the SOC and debate regarding Rashba effects in all-inorganic metal halide perovskites, providing critical insight into the physical phenomena and potential applications. Meanwhile, crystal structures and photophysics of all-inorganic perovskite are discussed in the context of SOC, along with the related experimental and characterization techniques. Furthermore, a recent understanding of the band topology in the all-inorganic halide perovskites is introduced to push the boundary even further for the novel applications of all-inorganic halide perovskites. Finally, an outlook is given on the potential directions of breakthroughs via leveraging the SOC in halide perovskites.

Using density functional theory-based first-principles simulations, detailed physical properties of the tetragonal phase alkali metal halide Rb2NbCl6 under pressure were explored for the first time. The structural, mechanical, and thermodynamic stability were confirmed by the Born stability requirements and the negative values for the formation energy. The analysis of Pugh’s and Poisson’s ratios and Cauchy’s pressure reveals that Rb2NbCl6 is ductile under the pressures in consideration. As the applied pressure rises, the elastic moduli show a rising trend, which indicates that Rb2NbCl6 stiffens up. According to several anisotropy indices, the compound is noticeably anisotropic both in ambient and under pressure. The machinability index suggests that the material under study is highly machinable. Several mechanical features of Rb2NbCl6 are analyzed according to the results of elastic constants and adequately explained. Since the melting temperature rises with applied pressure, Rb2NbCl6 is more suitable for high-temperature applications. The computed total density of states (TDOS) at 0 GPa pressure at EF is ∼5.07 states/eV/f.u., and applied pressure has a negligible effect on the value of DOS. The study of electronic properties provides significant support for interpreting the optical function. As the applied pressure rises, the reflectivity and absorption spectra shift to higher energy regions. High-reflectivity spectra suggest that the material would be an excellent choice for coatings that lower solar heating. The authors of this study expect that the fascinating findings of this investigation will give researchers and engineers a helpful foundation.