First‐Principles Investigation of Zn Doping Impacts on the Structural, Electronic, Mechanical, Thermodynamic, and Optical Properties of α‐NiS for Photocatalytic Activity

This study employs first‐principles calculations to investigate the effects of Zn doping on the structural, electronic, mechanical, thermodynamics, and optical properties of α‐NiS, targeting its enhancement for photocatalytic applications. Structural analysis reveals lattice expansion with increasing Zn concentration due to atomic size mismatch, while negative formation energies confirm thermodynamic stability. Ab initio molecular dynamics simulations at 500 K demonstrate excellent thermal stability for all doped systems. Zn doping effectively narrows the bandgap from 2.12 eV (pure) to 1.38 eV (37.5% Zn), improving visible‐light absorption and preserving p‐type conductivity. Mechanical analysis shows all compositions are stable and ductile, with reduced stiffness upon doping. Thermodynamic properties indicate enhanced entropy and heat capacity with Zn content, supporting improved thermal performance. Optical results show increased dielectric function, refractive index, and absorption in the visible range with doping. These findings highlight Zn‐doped α‐NiS as a promising, tunable material for efficient photocatalysis.