|
|
| Line 5: |
Line 5: |
| LIBXC1 and LIBXC2 can be either integers (e.g, 101 for PBE exchange) or strings (e.g., GGA_X_PBE). The list | | LIBXC1 and LIBXC2 can be either integers (e.g, 101 for PBE exchange) or strings (e.g., GGA_X_PBE). The list |
|
| |
|
| The amount of LDA correlation included in the hybrid functional can be specified through the {{TAG|ALDAC}}-tag.
| |
|
| |
|
| 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}}).
| |
|
| |
| '''Note''': The defaults are chosen such that the hybrid PBE0 functional is selected for PBE pseudopotentials (the PBE0 functional contains 25% of the exact exchange, and 75% of the PBE exchange, and 100% of the PBE correlation energy). The resulting expression for the exchange-correlation energy then takes the following simple form:
| |
|
| |
| <math>
| |
| E_{\mathrm{xc}}^{\mathrm{PBE0}}=\frac{1}{4}~E_{\mathrm{x}}~+
| |
| ~\frac{3}{4}~ E_{\mathrm{x}}^{\mathrm{PBE}}
| |
| +~E_{\mathrm{c}}^{\mathrm{PBE}}
| |
| </math>
| |
|
| |
| Other sensible values are of course {{TAG|AEXX}}=1.0 (full Hartree-Fock type calculations). In this case, VASP also automatically selects {{TAG|ALDAC}}=0.0 and {{TAG|AGGAC}}=0.0, to avoid the addition of a (semi-local) correlation energy.
| |
|
| |
| A comprehensive evaluation of the performance of the PBE0 functional, as compared to PBE, can be found in Ref. <ref name="paier:jcp:05"/>.
| |
|
| |
|
| <references> | | <references> |
| <ref name="paier:jcp:05">[https://aip.scitation.org/doi/10.1063/1.1926272 J. Paier, R. Hirschl, M. Marsman, and G. Kresse, J. Chem. Phys. 122, 234102 (2005).]</ref> | | <ref name="lehtola:sx:18">[https://doi.org/10.1016/j.softx.2017.11.002 S. Lehtola, C. Steigmann, M. J. T. Oliveira, and M. A. L. Marques, SoftwareX 7, 1 (2018).]</ref> |
| </references> | | </references> |
|
| |
|
Revision as of 14:38, 20 December 2021
LIBXC1/LIBXC2 = [integer] or string
Description: LIBXC1/LIBXC2 specify the functionals from the library of exchange-correlation functionals that one wants to use.
LIBXC1 and LIBXC2 can be either integers (e.g, 101 for PBE exchange) or strings (e.g., GGA_X_PBE). The list
Cite error: <ref> tag with name "lehtola:sx:18" defined in <references> is not used in prior text.
Related Tags and Sections
AGGAX,
AGGAC,
ALDAC,
LHFCALC,
hybrid functionals,
settings for specific hybrid functionals
Examples that use this tag
