Density functional theory (DFT) is a computational quantum mechanical modeling used in physics, chemistry, and materials science to evaluate the electronic structure (or nuclear structure, principally the ground state) of many-body systems, in particular atoms, molecules, and the condensed phases. A many-electron system's properties can be determined using functionals, i.e., functions of another function. In the case of DFT, these are functionals of the spatially dependent electron density. DFT is among the most popular and versatile methods available in condensed-matter physics, computational physics, and computational chemistry.