First-Principles Statistical Investigation of Thermodynamic Behavior with Excitonic Effects in Mo1-xWxSe2 Alloys through a Data-Driven Workflow Approach
Abstract
We investigate thermodynamic stability of the Mo1-xWxSe2 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 Mo1-xWxSe2 alloy, we find a non-linear dependence of the optical band gap on 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 Mo1-xWxSe2 alloys and their derivatives, providing an outstanding perspective for next-generation optoelectronic materials.