The minimal supercells approach for ab-initio calculation in 2D alloying transition metal dichalcoginides with special quasi-random structure

Abstract

Density functional theory (DFT) is used to investigate MoS _2 and WS _2 monolayers, which are direct bandgap semiconductors. We study alloying between MoS _2 and WS _2 by using special quasi-random structure (SQS), through a comparison of the computed pair distribution functions with various sizes of supercells. Our calculations show that a model 3 × 3 × 1 supercell structure of pseudobinary alloy Mo _1 _−x W _x S _2 can be correctly performed for energy and electronic band structure calculations. DFT is combined with SQS and reveals that alteration of the W concentration supports the band edges and energy gap. The electronic structure of Mo _1 _−x W _x S _2 clearly supports the results from the experimental observation as well as Monte Carlo simulation. Consequently, our model suggests that the generated alloy $M{o}_{x}{W}_{1-x}{S}_{2}$ monolayer with small supercells via SQS can clearly explain the behaviour of this material, using a low computational time but achieving good agreement with the experiment.

Keywords

• density functional theory
• transition metal dichalcogenide monolayer
• alloy
• spacial quasirandom structure