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On site Coulomb interaction: L(S)DA+U

Supported only by VASP.4.6 and on. THIS FEATURE IS IN LATE BETA STAGE (BUGS ARE POSSIBLE).

The L(S)DA often fails to describe systems with localized (strongly correlated) $d$ and $f$ electrons (this manifests itself primarily in the form of unrealistic one-electron energies). In some cases this can be remedied by introducing a strong intra-atomic interaction in a (screened) Hartree-Fock like manner, as an on site replacement of the L(S)DA. This approach is commonly known as the L(S)DA+U method.

VASP allows one to choose between two different approaches to L(S)DA+U:

The L(S)DA+U in VASP is switched on by means of the following tags

NB: LDAUL, LDAUU, and LDAUJ must be specified for all atomic species!

It is important to be aware of the fact that when using the L(S)DA+U, in general the total energy will depend on the parameters $U$ and $J$. It is therefore not meaningful to compare the total energies resulting from calculations with different $U$ and/or $J$ [c.q. $(U-J)$ in case of Dudarev's approach].

Note on bandstructure calculation: The CHGCAR file also contains only information up to LMAXMIX for the on-site PAW occupancy matrices. When the CHGCAR file is read and kept fixed in the course of the calculations ( ICHARG=11), the results will be necessarily not identical to a selfconsistent run. The deviations can be (or actually are) large for L(S)DA+U calculations. For the calculation of band structures within the L(S)DA+U approach, it is hence strictly required to increase LMAXMIX to 4 (d elements) and 6 (f elements). (see Sec. 6.56).


next up previous contents
Next: HF type calculations Up: The INCAR File Previous: Constraining the direction of   Contents
Georg Kresse
2009-04-23