Advanced Physical Research

Chemical substitution offers a powerful route for engineering electronic phases in two-dimensional (2D) van der Waals materials, particularly in systems where structural distortions and ligand-field asymmetry strongly influence electronic behavior. In this work, we perform a comprehensive first-principles investigation of pristine and Fe-substituted monolayer CrPSe₃ to elucidate the structural and electronic mechanisms that drive its semiconductor-to-metal transition. The optimized pristine structure reproduces experimentally reported bond lengths and angular distortions, confirming the reliability of our computational baseline. Fe incorporation induces pronounced anisotropic lattice relaxation, including a substantial reduction in the monoclinic angular disparity of the honeycomb network and significant reorganization of metal–chalcogen bonding. Charge-state analysis shows that Fe donates considerably fewer electrons to Se than Cr, enhancing Fe–Se covalency and shifting Fe 3d states into the narrow band gap of pristine CrPSe₃. These structural and chemical perturbations collectively increase p–d hybridization, broaden frontier bands, and generate a metallic electronic structure characterized by hybrid Fe/Cr t_2g states crossing the Fermi level. The results establish a coherent mechanistic framework linking lattice symmetry, bonding character, and orbital hierarchy, and demonstrate that the transition-metal substitution provides an effective pathway for tuning electronic phases in MPX₃ monolayers.