LTBOUNDLIBXC: Difference between revisions

Revision as of 19:20, 12 January 2022

TBOUNDLIBXC = .TRUE. | .FALSE.
Default: TBOUNDLIBXC = .FALSE.

Description: TBOUNDLIBXC specifies whether or not the lower bound for the Kohn-Sham kinetic-energy density $\tau_{\sigma}$ ( $\tau_{\sigma}^{\textrm{W}}<\tau_{\sigma}$ ) is enforced before $\tau_{\sigma}$ is used in a meta-GGA functional from Libxc.

The Kohn-Sham kinetic-energy density $\tau_{\sigma}$ should in principle be larger than the von Weizsäcker kinetic-energy density $\tau_{\sigma}^{\textrm{W}}=\left\vert\nabla\rho_{\sigma}\right\vert^{2}/\left(8\rho_{\sigma}\right)$ . However, for numerical reasons this may not always be the case and can potentially lead to problems depending on the meta-GGA. If TBOUNDLIBXC=.TRUE., then $\tau_{\sigma}=\max(\tau_{\sigma},\tau_{\sigma}^{\mathrm{W}})$ is applied before $\tau_{\sigma}$ is used in a meta-GGA functional from Libxc.

However, according to tests, for some of the most common meta-GGA functionals like SCAN^[1] a violation of the lower bound is technically not a problem and, furthermore, applying $\tau_{\sigma}=\max(\tau_{\sigma},\tau_{\sigma}^{\mathrm{W}})$ leads to very inaccurate forces and stress tensor.

Related Tags and Sections

LIBXC1, METAGGA

Examples that use this tag

↑ J. Sun, A. Ruzsinszky, and J. P. Perdew, Phys. Rev. Lett. 115, 036402 (2015).

[sun:prl:15-1] J. Sun, A. Ruzsinszky, and J. P. Perdew, Phys. Rev. Lett. 115, 036402 (2015).

[1]

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 The Kohn-Sham kinetic-energy density <math>\tau_{\sigma}</math> should in principle be larger than the von Weizsäcker kinetic-energy density <math>\tau_{\sigma}^{\textrm{W}}=\left\vert\nabla\rho_{\sigma}\right\vert^{2}/\left(8\rho_{\sigma}\right)</math>. However, for numerical reasons this may not always be the case and can potentially lead to problems depending on the meta-GGA. If {{TAG|TBOUNDLIBXC}}=.TRUE., then <math>\tau_{\sigma}=\max(\tau_{\sigma},\tau_{\sigma}^{\mathrm{W}})</math> is applied before <math>\tau_{\sigma}</math> is used in a meta-GGA functional from Libxc.
-However, according to tests, for some of the most common meta-GGA functionals like SCAN{{cite|sun:prl:15}} a violation of the lower bound is technically not a problem, and furthermore, applying <math>\tau_{\sigma}=\max(\tau_{\sigma},\tau_{\sigma}^{\mathrm{W}})</math> leads to very inaccurate forces and stress tensor.
+However, according to tests, for some of the most common meta-GGA functionals like SCAN{{cite|sun:prl:15}} a violation of the lower bound is technically not a problem and, furthermore, applying <math>\tau_{\sigma}=\max(\tau_{\sigma},\tau_{\sigma}^{\mathrm{W}})</math> leads to very inaccurate forces and stress tensor.
 == Related Tags and Sections ==