This research builds a DFT/VASP workflow to study how metallic Ag clusters (Ag₁–Ag₅) form and stabilize on Ag₃PO₄ surfaces and how they affect O₂ adsorption, linking surface thermodynamics to catalytic/photocatalytic reactivity. It benchmarks bulk reference energies, compares multiple surface terminations (ST1–ST6) via surface energies to select the most stable slab, then evaluates cluster stability and O₂ adsorption geometries/energies, supported by Python automation for slab/supercell preparation and post-processing of key descriptors such as work function and Ag d-band center