LNOAUGXC

LNOAUGXC = .TRUE. | .FALSE.
Default: LNOAUGXC = .FALSE.

Description: LNOAUGXC specifies if a METAGGA exchange-correlation functional is evaluated with a density that is augmented or not.

The Kohn-Sham kinetic-energy density $\tau_{\sigma}=(1/2)\sum_{i}\nabla\psi_{i\sigma}^{*}\cdot\nabla\psi_{i\sigma}$ should in principle be larger than the von Weizsäcker kinetic-energy density $\tau_{\sigma}^{\textrm{W}}=\left\vert\nabla\rho_{\sigma}\right\vert^{2}/\left(8\rho_{\sigma}\right)$ .^[1] However, this may not be always the case, in particular within the PAW spheres when the pseudo density is augmented with the compensation charge. If LNOAUGXC=.TRUE. in INCAR, then the pseudo density is not augmented, which should alleviate the breaking of the condition $\tau_{\sigma}^{\textrm{W}}<\tau_{\sigma}$ .

Not having $\tau_{\sigma}^{\textrm{W}}<\tau_{\sigma}$ satisfied can make the calculations unstable, in particular with the TPSS family of functionals.

Mind:

This tag is available since VASP.6.5.0 and is a replacement of the compiler option -DnoAugXCmeta that was available until VASP.6.4.3.
This option may negatively affect the results, therefore it should be used only for functionals, e.g. TPSS, for which the breaking of the condition $\tau_{\sigma}^{\textrm{W}}<\tau_{\sigma}$ may lead to numerical problems.

See LTBOUNDLIBXC for a related tag.

References

↑ S. Kurth, J. P. Perdew, and P. Blaha, Molecular and solid-state tests of density functional approximations: LSD, GGAs, and meta-GGAs, Int. J. Quantum Chem. 75, 889 (1999).

[kurth:ijqc:1999-1] S. Kurth, J. P. Perdew, and P. Blaha, Molecular and solid-state tests of density functional approximations: LSD, GGAs, and meta-GGAs, Int. J. Quantum Chem. 75, 889 (1999).

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Related tags and articles

References