The KKR formulation of DFT rephrases the usual eigenvalue-eigenvector problem (i.e. solving some effective Schrödinger equation) into an electronic scattering problem. It does so by partitioning the one-electron potential of DFT into a collection of spatially-localised potentials around each ionic site, before considering an electron propagating through the system and scattering from these localised potentials. In this manner, the Green's function of the system is obtained. In a system where there is lattice-based disorder (for example, in a substitutional alloy) the CPA provides a means by which to average multiple potentials associated with a single lattice site and obtain an average Green's function (and consequent electron density) in a physically meaningful way. Although the approach was originally formulated for potentials described within either the muffin tin or atomic sphere approximations (where the spatially localised potential is assumed spherically symmetric) it is now commonplace to use so-called full-potential calculations, where the one-electron potential can have arbitrary spatial dependence.