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}},
-The amount of gradient correction to the exchange and the correlation contributions can be set indepently, however (some [[specific_hybrid_functionals|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}}).
+{{TAG|ALDAC}},
-== Related Tags and Sections ==
 {{TAG|AGGAX}},
 {{TAG|AGGAC}},
-{{TAG|ALDAC}},
+{{TAG|AMGGAX}},
+{{TAG|AMGGAC}},
 {{TAG|LHFCALC}},
-[[Hartree-Fock_and_HF/DFT_hybrid_functionals|hybrid functionals]],
+{{TAG|HFSCREEN}},
-[[specific_hybrid_functionals|settings for specific hybrid functionals]]
+[[List_of_hybrid_functionals|List of hybrid functionals]],
+[[Hybrid_functionals:_formalism|Hybrid functionals: formalism]]
 {{sc|AEXX|Examples|Examples that use this tag}}
-== Example Calculations using this Tag ==
+== References ==
-{{TAG|bandgap of Si using different DFT+HF methods}}, {{TAG|Equilibrium volume of Si in the RPA}}, {{TAG|MgO optimum mixing}}, {{TAG|Model BSE calculation on Si}}, {{TAG|Si bandstructure}}, {{TAG|Si HSE bandstructure}}
+<references/>
 ----
-[[The_VASP_Manual|Contents]]
+[[Category:INCAR tag]][[Category:Exchange-correlation functionals]][[Category:Hybrid_functionals]]
-[[Category:INCAR]][[Category:Hybrids]]