Structural Distortions and Energy Band Structure of Ag‐Doped As2S3 and Ag2S3

Abstract

The density functional theory (DFT) with generalized gradient approximation (GGA) for exchange correlation potential as incorporated within SIESTA code is used to investigate the structural distortions and energy bands of AgxAs2 – xS3 (x = 0–2). The lattice parameters and cell volume change asymmetrically with an increase in Ag concentration due to asymmetric changes in electrostatic and strain field interactions. The optimized lattice geometry of As2S3, Ag1As1S3, and Ag2S3 is monoclinic, whereas for other configurations, it becomes triclinic. Unlike Ag2S3, the layering is not found in the structure of Ag2S3. The mobility gap decreases and then increases with an increase in Ag concentration. The minimum value of mobility gap is 0.04 eV for the configuration Ag1As1S3. The partial density of states (PDOS) of d orbital electrons significantly enhances with an increase in Ag concentration, and the structural changes in PDOS of s, p, and d orbital electrons suggest the weak and strong p–d hybridizations in valence and conduction bands, respectively. The reduction in the mobility gap suggests that Ag‐doped As2S3 is more conducting than As2S3 as observed experimentally.