## Construction of the potential

Just like the charge density the effective potential is also represented in a region-dependent way as

For the potential the interstitial region and the vacuum regions the plane-wave expansion is limited by the $G_\text{max}$ cutoff specified in calculationSetup/cutoffs/@Gmax. The spherical harmonics expansion in the MT spheres is limited by the $l_\text{max}^\alpha$ cutoffs specified for each species in atomSpecies/species/atomicCutoffs/@lmax

As a sum of the Hartree potential, the external potential, and the exchange-correlation potential it is given by

The construction of the Hartree potential together with the external potential involves neither approximations nor special input parameters. It is therefore neglected in this discussion. For details on this part of the calculation see M. Weinert, Solution of Poisson's equation: Beyond Ewaldtype methods, JMP 22, 2433 (1981).

### The exchange-correlation potential

(To be discussed: GmaxXC, choice of functional, relativisticCorrections)