# Category:DFT+U

The LDA and semilocal GGA functionals often fail to describe systems with localized (strongly correlated) or electrons (this manifests itself primarily in the form of unrealistic one-electron energies or too small magnetic moments). In some cases this can be remedied by introducing on the or atom a strong intra-atomic interaction in a simplified (screened) Hartree-Fock like manner (), as an on-site replacement of the LDA/GGA functional:

where is the double-counting term and is the on-site occupancy matrix of the or electrons. This approach is known as the DFT+U method (traditionally called LSDA+U^{[1]}).

The first VASP DFT+U calculations, including some additional technical details on the VASP implementation, can be found in Ref. ^{[2]} (the original implementation was done by Olivier Bengone ^{[3]} and Georg Kresse).

For more details, read the article about the formalism of the DFT+U method.

## How to

DFT+U can be switched on with the LDAU tag, while the LDAUTYPE tag determines the DFT+U flavor that is used. LDAUL specifies the -quantum number for which the on-site interaction is added, and the effective on-site Coulomb and exchange interactions are set (in eV) with the LDAUU and LDAUJ tags, respectively. Note that it is recommended to increase LMAXMIX to 4 for *d*-electrons or 6 for *f*-elements.