LTHOMAS: Difference between revisions

Latest revision as of 11:55, 19 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 exponential screening. The Thomas-Fermi screening length k_TF 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

Mind: If LTHOMAS=.TRUE., then LHFCALC=.TRUE. is automatically set.

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.

@@ Line 1: / Line 1: @@
 {{TAGDEF|LTHOMAS|.TRUE. {{!}} .FALSE.|.FALSE.}}
-Description: {{TAG|LTHOMAS}}
+Description: {{TAG|LTHOMAS}} selects a decomposition of the exchange functional based on Thomas-Fermi exponential screening.
 ----
-== Related Tags and Sections ==
+If {{TAG|LTHOMAS}}=.TRUE. the decomposition of the exchange operator (in a [[Hybrid functionals: formalism|range-separated hybrid functional]]) into a short range and a long range part will be based on Thomas-Fermi exponential screening.
+The Thomas-Fermi screening length ''k''<sub>TF</sub> is specified by means of the {{TAG|HFSCREEN}} tag.
+For typical semiconductors, a Thomas-Fermi screening length of about 1.8 &Aring;<sup>-1</sup> 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 {{FILE|POTCAR}} file) and the volume and writes the corresponding value to the {{FILE|OUTCAR}} file:
+  Thomas-Fermi vector in A             =   2.00000
+{{NB|mind|If {{TAG|LTHOMAS}}{{=}}.TRUE., then {{TAG|LHFCALC}}{{=}}.TRUE. is automatically set.}}
+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 ==
 {{TAG|LHFCALC}},
 {{TAG|HFSCREEN}},
-[[Hartree-Fock_and_HF/DFT_hybrid_functionals|hybrid functionals]],
+{{TAG|LRHFCALC}},
-[[Hartree-Fock_and_HF/DFT_hybrid_functionals#range_separated|range separated hybrid functionals]],
+[[Hybrid functionals: formalism#Thomas-Fermi exponential screening with short-range Hartree-Fock exchange|Thomas-Fermi screening]],
-[[specific_hybrid_functionals|settings for specific hybrid functionals]]
+[[list_of_hybrid_functionals|List of hybrid functionals]],
+[[Hybrid_functionals:_formalism|Hybrid functionals: formalism]]
+{{sc|LTHOMAS|Examples|Examples that use this tag}}
 ----
-[[The_VASP_Manual|Contents]]
-[[Category:INCAR]][[Category:Hybrids]]
+[[Category:INCAR tag]][[Category:Exchange-correlation functionals]][[Category:Hybrid_functionals]]