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 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.