LTBOUNDLIBXC

From VASP Wiki

LTBOUNDLIBXC = .TRUE. | .FALSE.
Default: LTBOUNDLIBXC = .FALSE. 

Description: LTBOUNDLIBXC specifies whether or not the lower bound for the Kohn-Sham kinetic-energy density () is enforced before is used in a METAGGA functional from Libxc.


The Kohn-Sham kinetic-energy density

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

However, for numerical reasons this may not always be the case and can potentially lead to problems depending on the meta-GGA. If LTBOUNDLIBXC=.TRUE. in INCAR, then is applied before is used in a meta-GGA functional from Libxc.

However, according to tests, for some of the most common meta-GGA functionals like SCAN[2], a violation of the lower bound is technically not a problem and, furthermore, applying leads to very inaccurate forces and stress tensor. Therefore, by default LTBOUNDLIBXC=.FALSE. and Libxc should be compiled with the option --disable-fhc has explained here.

Related tags and articles

LIBXC1, LIBXC2, METAGGA


Examples that use this tag

References