Effect of pressure on structural properties and energy band gaps of γ‐InSe

Abstract

AbstractWe have investigated theoretically the effect of hydrostatic pressure on interatomic bond lengths and energy band gaps of γ‐InSe. Total energy calculations were performed using the linear augmented plane wave (LAPW) method, taking into account scalar relativistic corrections as well as spin‐orbit coupling. Internal structural parameters were optimized for different pressures by adopting as input the unit cell parameters known from experiment. Our theoretical results for the nearest‐neighbor In–Se bond length are in excellent agreement with a recent experimental determination from high‐pressure EXAFS measurements. The covalent In–In bond is found to be more compressible than the partially ionic In–Se bond. We also present the calculated pressure dependence of band gaps and compare to recent high‐pressure experimental studies of optical and transport properties. A large negative pressure coefficient is obtained for the indirect Z–A gap. This leads to a crossover from a direct to an indirect fundamental gap within the stability range of the γ‐polytype of InSe, in qualitative agreement with recent experiments.