LTHOMAS: Difference between revisions
No edit summary |
No edit summary |
||
| Line 1: | Line 1: | ||
{{TAGDEF|LTHOMAS|.TRUE. {{!}} .FALSE.|.FALSE.}} | {{TAGDEF|LTHOMAS|.TRUE. {{!}} .FALSE.|.FALSE.}} | ||
Description: {{TAG|LTHOMAS}} selects a decomposition of the exchange functional based on Thomas-Fermi screening. | Description: {{TAG|LTHOMAS}} selects a decomposition of the exchange functional based on Thomas-Fermi exponential screening. | ||
---- | ---- | ||
If {{TAG|LTHOMAS}}=.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. | If {{TAG|LTHOMAS}}=.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. | ||
Revision as of 19:47, 17 October 2023
LTHOMAS = .TRUE. | .FALSE.
Default: LTHOMAS = .FALSE.
Description: LTHOMAS selects a decomposition of the exchange functional based on Thomas-Fermi exponential screening.
If LTHOMAS=.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 articles
LHFCALC, HFSCREEN, Thomas-Fermi screening, List of hybrid functionals