Pressure-driven structural and electronic transitions in a quasimolecular layered compound of antimony triiodide

Abstract

Quasimolecular layered metal triiodides MI₃ (M = Sb and Bi) hold immense promise in applications of solid-state batteries, radiation detectors, and photocatalysts owing to their favorable physicochemical properties. As a representative MI₃ compound, antimony triiodide (SbI₃) exhibits high-pressure phase stability beyond 16.0 GPa and its electrical transport behaviors remain largely unknown. In this study, we systemically investigated the structural and electronic transitions of SbI₃ during compression and decompression under different hydrostatic environments using synchrotron X-ray diffraction, Raman spectroscopy, electrical conductivity, and first-principles theoretical calculations. During compression, SbI₃ endured two isostructural phase transitions (IPTs) at the respective pressures of 3.4 GPa and 10.3 GPa stemming from the prominent compression of the c-axis and Sb–I bond. Upon further compression to 32.3 GPa, an electronic transition from the semiconductor to metal occurred in SbI₃ under non-hydrostatic conditions, which was possibly associated with the rhombohedral (R)-to-monoclinic (C2/m) structural transformation. Under hydrostatic conditions, a considerable pressure hysteresis of ∼5.0 GPa was detected for the emergence of metallization owing to the faint deviatoric stress. During decompression, the phase transition of SbI₃ was revealed to be irreversible under different hydrostatic environments, which was probably caused by the huge kinetic barrier for the continuous high-pressure structural transitions. Our high-pressure study on SbI₃ offers an in-depth insight into the correlations between crystalline and electronic structures, and may facilitate the application of quasimolecular layered crystals in optoelectronic devices.