1：Experimental Design and Method Selection

First principles methods based on density functional theory and beyond were employed to study CdSexTe1?x alloys. The cluster expansion formalism was used to provide a detailed phase diagram. Disordered CdSexTe1?x configurations were modeled using special quasirandom structures, and optoelectronic properties were computed with the hybrid HSE06 functional.

2：Sample Selection and Data Sources

CdSexTe1?x alloys in the zincblende and wurtzite structures were studied. The samples were modeled using special quasirandom structures at concentrations of x = 0.25, 0.50, and 0.75.

3：List of Experimental Equipment and Materials

Vienna Ab initio Simulation package (VASP) was used for all density functional theory calculations. The projector augmented wave (PAW) method was employed with the generalized gradient approximation (GGA) in the form of the Perdew-Burke-Ernzerhof (PBE) exchange-correlation functional.

4：Experimental Procedures and Operational Workflow

Calculations were carried out on Γ-centered k-point meshes consisting of 4000 k-points per reciprocal atom (KPPRA). Electronic minimizations with a convergence criterion of 10?6 eV/atom were performed using the tetrahedron method with Bl?chl corrections. Initial structural configurations of CdTe and CdSe in the zincblende and wurtzite structures were taken from the Materials Project and geometrically optimized until forces acting on each atom were less than 0.01 eV/?.

5：Data Analysis Methods

The electronic density of states (DOS) and frequency-dependent complex dielectric function (ε1 + iε2) for each compound were calculated. From the latter values, derived optical properties such as absorption coefficient and reflectivity were determined. Effective masses of electrons and holes were calculated using the BoltzTraP package.