First-principles statistical investigation of thermodynamic behavior with excitonic effects in Mo1−xWxSe2 alloys through a data-driven workflow approach

Abstract

We investigate the thermodynamic stability of the Mo_1−xW_xSe₂ alloy at the atomistic level and introduce an innovative cost-effective protocol for predicting and characterizing its optoelectronic properties, explicitly incorporating excitonic effects. Herein, the proposed protocol is implemented within an automated workflow approach through the Simstack framework to address the reproducibility and transferability of the data, enabling a theoretical description of a random alloy model within a statistical ensemble (based on the generalized quasi-chemical approximation) throughout a complete composition range and a wide temperature spectrum. Thus, by statistically averaging over the configurational ensemble of the Mo_1−xW_xSe₂ alloy, we find a non-linear dependence of the optical band gap on the alloy composition. In particular, W-rich compositions exhibit pronounced spin–orbit coupling (SOC) effects, which significantly modify the band structure and indirectly influence the optical absorption anisotropy observed along in-plane directions of the monolayer. In addition, SOC effects in W-rich compositions lead to an increase in the optical band gap and a concurrent decrease in exciton binding energy, primarily due to enhanced spin–orbit splitting and modified electronic band curvatures. Our thermodynamic and optoelectronic analysis offers a robust and efficient protocol for the rational design of Mo_1−xW_xSe₂ alloys and their derivatives, providing an outstanding perspective for next-generation optoelectronic materials.