A layered rhombohedral polymorph of indium (III) triiodide is synthesized at high pressure and temperature. The unit cell symmetry and approximate dimensions are determined by single crystal X-ray diffraction. Its R-3 crystal structure, with a = 7.217 {\AA}, and c = 20.476 {\AA}, is refined by the Rietveld method on powder X-ray diffraction data. The crystal structure is based on InI6 octahedra sharing edges to form honeycomb lattice layers, though with considerable stacking variations. Different from ambient pressure InI3, which has a monoclinic molecular structure and a light-yellow color, high pressure InI3 is layered and has an orange color. The band gaps of both the monoclinic and rhombohedral variants of InI3 are estimated from diffuse reflectance measurements.
@article{arxiv.2311.04332,
title = {The Pressure-Stabilized Polymorph of Indium Triiodide},
author = {Danrui Ni and Haozhe Wang and Xianghan Xu and Weiwei Xie and Robert J. Cava},
journal= {arXiv preprint arXiv:2311.04332},
year = {2023}
}