Electronic structure, linear, nonlinear optical susceptibilities and birefringence of CuInX2 (X = S, Se, Te) chalcopyrite-structure compounds

TL;DR

This study uses advanced computational methods to analyze the electronic and optical properties of CuInX2 chalcopyrite crystals, revealing their semiconducting nature, birefringence characteristics, and nonlinear optical susceptibilities, with results aligning with experimental data.

Contribution

It provides detailed first-principles calculations of electronic structure, birefringence, and nonlinear optical susceptibilities for CuInX2 compounds, highlighting how substituting chalcogen elements affects these properties.

Findings

CuInS2 and CuInSe2 have negative birefringence; CuInTe2 has positive birefringence.

Smaller band gaps correlate with larger nonlinear susceptibilities.

Optical susceptibilities increase with Se substitution and decrease with Te substitution.

Abstract

The electronic structure, linear and nonlinear optical properties have been calculated for CuInX2 (X=S, Se, Te) chalcopyrite-structure single crystals using the state-of-the-art full potential linear augmented plane wave (FP-LAPW) method. We present results for band structure, density of states, and imaginary part of the frequency-dependent linear and nonlinear optical susceptibilities. We find that these crystals are semiconductors with direct band gaps. We have calculated the birefringence of these crystals. The birefringence is negative for CuInS2 and CuInSe2 while it is positive for CuInTe2 in agreement with the experimental data. Calculations are reported for the frequency-dependent complex second-order non-linear optical susceptibilities . The intra-band and inter-band contributions to the second harmonic generation increase when we replace S by Se and decrease when we replace Se by Te. We find that smaller energy band gap compounds have larger values of in agreement with the experimental data and previous theoretical calculations.