LNOAUGXC

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

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


The Kohn-Sham kinetic-energy density

[math]\displaystyle{ \tau_{\sigma}=\frac{1}{2}\sum_{i}\nabla\psi_{i\sigma}^{*}\cdot\nabla\psi_{i\sigma} }[/math]

should, in principle, be larger than the von Weizsäcker kinetic-energy density[1]

[math]\displaystyle{ \tau_{\sigma}^{\textrm{W}}=\frac{\left\vert\nabla n_{\sigma}\right\vert^{2}}{8 n_{\sigma}}. }[/math]

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 [math]\displaystyle{ \tau_{\sigma}^{\textrm{W}}\lt \tau_{\sigma} }[/math].

A violation of [math]\displaystyle{ \tau_{\sigma}^{\textrm{W}}\lt \tau_{\sigma} }[/math] 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 [math]\displaystyle{ \tau_{\sigma}^{\textrm{W}}\lt \tau_{\sigma} }[/math] may lead to numerical problems.

Related tags and articles

METAGGA, LTBOUNDLIBXC

Examples that use this tag

References