LNOAUGXC

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

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

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The Kohn-Sham kinetic-energy density

$\tau_{\sigma}=\frac{1}{2}\sum_{i}\nabla\psi_{i\sigma}^{*}\cdot\nabla\psi_{i\sigma}$

should, in principle, be larger than the von Weizsäcker kinetic-energy density

$\tau_{\sigma}^{\textrm{W}}=\frac{\left\vert\nabla n_{\sigma}\right\vert^{2}}{8 n_{\sigma}}.$

However, this may not always be the case, particularly within the PAW spheres, when the pseudo density is augmented with the compensation charge. If LNOAUGXC=.TRUE. is set in the INCAR file, then the pseudo density is not augmented, which should alleviate the breaking of the condition $\tau_{\sigma}^{\textrm{W}}<\tau_{\sigma}$.

A violation of $\tau_{\sigma}^{\textrm{W}}<\tau_{\sigma}$ 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.

Related tags and articles

METAGGA, LTBOUNDLIBXC

Examples that use this tag