AEXX: Difference between revisions

Latest revision as of 08:28, 18 October 2023

AEXX = [real]

Default: AEXX	= 0.25	if LHFCALC=.TRUE.
	= 0	if LHFCALC=.FALSE.

Description: AEXX specifies the fraction of exact exchange in a Hartree-Fock-type/hybrid-functional calculation.

Mind:

For versions of VASP prior to 6.4.0, ALDAX was constrained to be equal to 1.0-AEXX. This constraint is lifted since VASP.6.4.0.
For AEXX=1.0, VASP switches off correlation by default (ALDAC=0.0, AGGAC=0.0, and AMGGAC=0.0) and thus runs a full Hartree-Fock calculation.

References

@@ Line 1: / Line 1: @@
 {{TAGDEF|AEXX|[real]}}
-{{DEF|AEXX|0.25|if {{TAG|LHFCALC}}{{=}}.TRUE.|0|otherwise}}
+{{DEF|AEXX|0.25|if {{TAG|LHFCALC}}{{=}}.TRUE.|0|if {{TAG|LHFCALC}}{{=}}.FALSE.}}
-Description: {{TAG|AEXX}} specifies the fraction of exact exchange in a Hartree-Fock/DFT hybrid functional type calculation.
+Description: {{TAG|AEXX}} specifies the fraction of exact exchange in a Hartree-Fock-type/hybrid-functional calculation.
 ----
-The sum of the fraction of the exact exchange and LDA exchange is always 1.0, and it is not possible to set the amount of LDA exchange indepently. Examples: if {{TAG|AEXX}}=0.25, 1/4 of the exact exchange is used, and 3/4 of the LDA exchange is added. For {{TAG|AEXX}}=0.5, half of the exact exchange is used, and one half of the LDA exchange is added.
+{{NB|mind|
+*For versions of VASP prior to 6.4.0, {{TAG|ALDAX}} was constrained to be equal to 1.0-{{TAG|AEXX}}. This constraint is lifted since VASP.6.4.0.
+*For {{TAG|AEXX}}{{=}}1.0, VASP switches off correlation by default ({{TAG|ALDAC}}{{=}}0.0, {{TAG|AGGAC}}{{=}}0.0, and {{TAG|AMGGAC}}{{=}}0.0) and thus runs a full Hartree-Fock calculation.}}
-The amount of LDA correlation included in the hybrid functional can be specified through the {{TAG|ALDAC}}-tag.
+== Related tags and articles ==
+{{TAG|ALDAX}},
+{{TAG|ALDAC}},
+{{TAG|AGGAX}},
+{{TAG|AGGAC}},
+{{TAG|AMGGAX}},
+{{TAG|AMGGAC}},
+{{TAG|LHFCALC}},
+{{TAG|HFSCREEN}},
+[[List_of_hybrid_functionals|List of hybrid functionals]],
+[[Hybrid_functionals:_formalism|Hybrid functionals: formalism]]
-The amount of gradient correction to the exchange and the correlation contributions can be set indepently, however (some popular hybride functionals for instance use only 0.8 of the gradient contribition to the exchange). The GGA flags {{TAG|AGGAX}} and {{TAG|AGGAC}} are only used if GGA is already selected (for LDA type calculations no gradient correction will be added regardless of values is used for {{TAG|AGGAX}} and {{TAG|AGGAC}}).
+{{sc|AEXX|Examples|Examples that use this tag}}
-== Related Tags and Sections ==
+== References ==
-{{TAG|AGGAX}},
+<references/>
-{{TAG|AGGAC}},
-{{TAG|ALDAC}}
 ----
-[[The_VASP_Manual|Contents]]
+[[Category:INCAR tag]][[Category:Exchange-correlation functionals]][[Category:Hybrid_functionals]]
-[[Category:INCAR]]