Hybrid functionals: Difference between revisions
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==VASP== | ==VASP== | ||
* For | * For all hybrid functional calculations, set: | ||
LHFCALC = .TRUE. | LHFCALC = .TRUE. | ||
* For HSE calculations, set the HFSCREEN parameter: | |||
HFSCREEN = 0.2 # HSE06 | |||
HFSCREEN = 0.3 # HSE03 | |||
The HFSCREEN parameter specifies the distance (in 1/Å) at which the exact (Hartree-Fock) exchange is screened. | |||
Therefore HF exact exchange is screened at a distance larger than 5 Å (HSE06), or 3.333 Å (HSE03), respectively, the way it is implemented in VASP. The difference between HSE03 and HSE06 is discussed in detail by Krukau et al. J. Chem. Phys. 125, 224106 (2006): https://aip.scitation.org/doi/abs/10.1063/1.2404663 | |||
* Defining the amount of introduced exact exchange: | |||
AEXX = 0.25 # Amount of exact HF exchange, ie. 25% | |||
AGGAX = 0.75 # Amount of GGA exchange, i.e. 75 % | |||
(. | This is the default setting with 25 % exact exchange, you may reduce that number, in particular if you have compounds with transition metals and/or degenerate electronic states (see theory above). | ||
* HSE03-13: This functional was optimised to fit the band gap of CoFe Prussian blue compounds; it generally presents a good compromise for calculating ionic solid compounds, which contain coordinated transition metal centres | |||
LHFCALC = .TRUE. | |||
HFSCREEN = 0.3 # HSE03 | |||
AEXX = 0.13 # Amount of exact HF exchange, ie. 13% | |||
AGGAX = 0.87 # Amount of GGA exchange, i.e. 87 % | |||
There are of course many other hybrid functionals, which require different settings, but generally they can be described by defining the GGA functional and the above-listed parameters. | |||
(see also: https://cms.mpi.univie.ac.at/wiki/index.php/Specific_hybrid_functionals) | |||
==Quantum Espresso== | ==Quantum Espresso== | ||
(...) | (...) | ||
Revision as of 13:16, 2 July 2019
go back to Main Page, Group Pages, Núria López and Group
This page is under edition, it may not make sense yet :) (feel free to ask, if you have questions)
Hybrid functional theory
tbd
Implementation
VASP
- For all hybrid functional calculations, set:
LHFCALC = .TRUE.
- For HSE calculations, set the HFSCREEN parameter:
HFSCREEN = 0.2 # HSE06 HFSCREEN = 0.3 # HSE03
The HFSCREEN parameter specifies the distance (in 1/Å) at which the exact (Hartree-Fock) exchange is screened. Therefore HF exact exchange is screened at a distance larger than 5 Å (HSE06), or 3.333 Å (HSE03), respectively, the way it is implemented in VASP. The difference between HSE03 and HSE06 is discussed in detail by Krukau et al. J. Chem. Phys. 125, 224106 (2006): https://aip.scitation.org/doi/abs/10.1063/1.2404663
- Defining the amount of introduced exact exchange:
AEXX = 0.25 # Amount of exact HF exchange, ie. 25% AGGAX = 0.75 # Amount of GGA exchange, i.e. 75 %
This is the default setting with 25 % exact exchange, you may reduce that number, in particular if you have compounds with transition metals and/or degenerate electronic states (see theory above).
- HSE03-13: This functional was optimised to fit the band gap of CoFe Prussian blue compounds; it generally presents a good compromise for calculating ionic solid compounds, which contain coordinated transition metal centres
LHFCALC = .TRUE. HFSCREEN = 0.3 # HSE03 AEXX = 0.13 # Amount of exact HF exchange, ie. 13% AGGAX = 0.87 # Amount of GGA exchange, i.e. 87 %
There are of course many other hybrid functionals, which require different settings, but generally they can be described by defining the GGA functional and the above-listed parameters.
(see also: https://cms.mpi.univie.ac.at/wiki/index.php/Specific_hybrid_functionals)
Quantum Espresso
(...)