Density functional theory (DFT) uses the Hohenberg-Kohn-Sham theory to map the many-body Schrödinger equation onto a single-body problem. VASP is a DFT software package that uses plane wave basis sets, pseudopotentials to approximate core electrons, and periodic boundary conditions to model materials with up to 200 atoms. VASP input files include INCAR for calculation parameters, POSCAR for geometry, POTCAR for pseudopotentials, and KPOINTS for k-point meshes.