Dear All,
I perform standard DFT calcualtion on a system. Now, I wish to have the energy correction with HSE06. In OUTCAR, only the total energy is givel. Is there any way to see the energy correction? Wish to see an early reply.
Thankis in advanced.
HSE06 energy correction
Moderators: Global Moderator, Moderator
-
pramanikanup
- Newbie
- Posts: 4
- Joined: Sun Aug 08, 2010 5:24 am
- License Nr.: 5-648
- Location: Santiniketan, India
HSE06 energy correction
Last edited by pramanikanup on Mon Dec 27, 2010 7:51 am, edited 1 time in total.
Anup Pramanik
-
sankh
- Newbie
- Posts: 24
- Joined: Sun Dec 19, 2010 1:42 am
- Location: Dublin, Ireland
HSE06 energy correction
Hey Anup,
The energy correction/change is:
E(cort) = E(local XC) - E(HSE-x-y),
where E(local XC) is the total energy of your system produced by the local XC functional that you used in a previous run, and E(HSE) is the total energy of your system produced by adding a certain x% of Fock exchange energy with a certain y% of truncation in Fock tail. If y = 20%, which means HFSCREEN = 0.2, you select HSE06 hybrid functionals with x% addition of Fock (with 20% truncation) to your reference local exchange-correlation potential. With AEXX tag you can select how much (x) trucated Fock contribution you wish to incorporate. Typically you can select AEXX = 0.25, which is equivalent to x = 25. Furthermore, there are tags which will allow you even to decide yourself how much GGA and LDA corrections you wish to incorporate to exchange (AGGAX tag) and correlation (AGGAC, ALDAC tags) if you were using a GGA XC functional but if you were using an LDA/LSDA XC functional, then you need not to worry about GGA corrections to exchange and correlation energies.
Having said these, I want to point out that from a Theoretical point of view, actually this is not a correction, as MPn corrects the Hartree-Fock energies by bringing in n-th order correlation energy to the HF (which 0-th order as there is "0" correlation energy included) reference. Within traditional KS-DFT description, adding any thing, such as GGA corrections, meta-GGA corrections, adding an amount of exact "non-local" exchange (which is Fock exchange), etc., to the exactly "local" exchange and correlation potentials changes the reference, as you substract out an equal part of the local terms. Without a fixed reference, one cannot talk about correction.
Please go through Axel Becke's papers on BLYP and 3 component B3LYP (a% local XC + b% GGA XC + c% Fock echange) functionals. E(BLYP) - E(B3LYP) cannot be said a correction to E(BLYP) due to addition of 25% of Fock exchange in B3LYP.
Hope it helps.
Cheers,
Sankh
The energy correction/change is:
E(cort) = E(local XC) - E(HSE-x-y),
where E(local XC) is the total energy of your system produced by the local XC functional that you used in a previous run, and E(HSE) is the total energy of your system produced by adding a certain x% of Fock exchange energy with a certain y% of truncation in Fock tail. If y = 20%, which means HFSCREEN = 0.2, you select HSE06 hybrid functionals with x% addition of Fock (with 20% truncation) to your reference local exchange-correlation potential. With AEXX tag you can select how much (x) trucated Fock contribution you wish to incorporate. Typically you can select AEXX = 0.25, which is equivalent to x = 25. Furthermore, there are tags which will allow you even to decide yourself how much GGA and LDA corrections you wish to incorporate to exchange (AGGAX tag) and correlation (AGGAC, ALDAC tags) if you were using a GGA XC functional but if you were using an LDA/LSDA XC functional, then you need not to worry about GGA corrections to exchange and correlation energies.
Having said these, I want to point out that from a Theoretical point of view, actually this is not a correction, as MPn corrects the Hartree-Fock energies by bringing in n-th order correlation energy to the HF (which 0-th order as there is "0" correlation energy included) reference. Within traditional KS-DFT description, adding any thing, such as GGA corrections, meta-GGA corrections, adding an amount of exact "non-local" exchange (which is Fock exchange), etc., to the exactly "local" exchange and correlation potentials changes the reference, as you substract out an equal part of the local terms. Without a fixed reference, one cannot talk about correction.
Please go through Axel Becke's papers on BLYP and 3 component B3LYP (a% local XC + b% GGA XC + c% Fock echange) functionals. E(BLYP) - E(B3LYP) cannot be said a correction to E(BLYP) due to addition of 25% of Fock exchange in B3LYP.
Hope it helps.
Cheers,
Sankh
Last edited by sankh on Tue Jan 18, 2011 5:10 am, edited 1 time in total.