For geometry optimizations and low-level band structure calculations, a gradient corrected local functional is sufficient, most prominently the PBE functional is employed, while band gaps should be improved using a hybrid approach, such as PBE0 or HSE06. For heavier nuclei, scalar relativistic effects can be treated either using the zero-order regular approximation (ZORA), relativistically corrected pseudo-potentials or effective-core potentials. DFT allows also the calculation of spin-spin couplings, which are necessary to account for magnetic ordering. In very demanding cases, wave-function based methods, such as complete active space self-consistent field (CASSCF) calculations, have been employed to accurately describe excited states. Beyond DFT. There are well-known limitations for electronic structure calculations using DFT, most notably the too-narrow band gaps. A thorough validation of using methods beyond DFT is, therefore, desirable, even though often impossible due to the computational costs. Options include the quasi-particle model GLLB-SC, which is available in AMS/BAND, and GW and RPA methods, as provided in FHI/aims and VASP.