LMODELHF
LMODELHF = .TRUE. | .FALSE.
Default: LMODELHF = .FALSE.
Description: LMODELHF selects a decomposition of the exchange functional based on a range separated screening, with full exchange in the short range, and AEXX in the long range.
If LMODELHF=.TRUE. the decomposition of the exchange operator (in a range separated hybrid functional) into a short range and a long range part will be based on Thomas-Fermi screening. The Thomas-Fermi screening length kTF is specified by means of the HFSCREEN tag.
For typical semiconductors, a Thomas-Fermi screening length of about 1.8 Å-1 yields reasonable band gaps. In principle, however, the Thomas-Fermi screening length depends on the valence electron density; VASP determines this parameter from the number of valence electrons (read from the POTCAR file) and the volume and writes the corresponding value to the OUTCAR file:
Thomas-Fermi vector in A = 2.00000
Since, VASP counts the semi-core states and d-states as valence electrons, although these states do not contribute to the screening, the values reported by VASP are often incorrect.
Related Tags and Sections
LHFCALC, HFSCREEN, hybrid functionals, Thomas-Fermi screening, settings for specific hybrid functionals