[CP2K-user] [CP2K:19368] Isolate dispersion contribution in vdW-DF2 calculations

[Jürg Hutter]

Hi

I cannot answer this question. I would suggest to check the papers where
these functionals have been proposed.

regards
JH

________________________________________
From: cp2k at googlegroups.com <cp2k at googlegroups.com> on behalf of Michael Fischer <doktorbrezel at gmail.com>
Sent: Monday, October 16, 2023 11:19 AM
To: cp2k
Subject: Re: [CP2K:19368] Isolate dispersion contribution in vdW-DF2 calculations

Dear Prof. Hutter,

Thank you very much for the clarification.
I presume that it cannot be expected that a simple "switching off" of the dispersion part (commenting out the entire vdW_POTENTIAL block and re-running a single-point calculation with the same combination of exchange and correlation functionals) would not give a physically meaningful estimation of the dispersion contribution (as the difference between "full" rev-vdW-DF2 energy and the "exchange-corellation only" energy), because some part of the local contribution is implicitly included in the exchange-correlation part. Or could that be a plausible option?

Thanks again, best regards,
Michael

Jürg Hutter schrieb am Montag, 16. Oktober 2023 um 11:08:42 UTC+2:
Hi

the printed dispersion energy is the calculated energy of the non-local
vdW energy functional (only the non-local part!). Together with the XC
energy you get the full functional energy. No other information is available.

regards
JH

________________________________________
From: cp... at googlegroups.com <cp... at googlegroups.com> on behalf of Michael Fischer <doktor... at gmail.com>
Sent: Friday, October 13, 2023 10:16 AM
To: cp2k
Subject: [CP2K:19362] Isolate dispersion contribution in vdW-DF2 calculations

Dear all,

I am studying host-guest systems (molecules in zeolites) with the rev-vdW-DF2 functional (X_B86_R, PW92 correlation, LMKLL dispersion) and I am looking at the possibility to calculate the dispersion contribution to the total interaction energy.

In the past, I have used Grimme-type dispersion correction, e.g., PBE-D3. Here, it was fairly trivial to calculate the dispersion contribution as:
E_disp = E_disp(host+guest) - E_disp(host) - E_disp(guest)
...where the E_disp terms on the right-hand side correspond to the energy values given in the line "Dispersion energy" in the CP2K output.

With rev-vdW-DF2, "Dispersion energy" is also printed. However, what is notable in the first place is that the dispersion energy is always positive. A subtraction as in the above equation gives results that look plausible at first, but a comparison to the total interaction energies shows that the E_disp contribution is sometimes more negative than E_tot, something which seems implausible.

Is there some way to isolate the dispersion contribution in calculations using non-local vdW-DF approximations?

Any suggestion will be highly appreciated!
Thank you and best regards,
Michael

--
You received this message because you are subscribed to the Google Groups "cp2k" group.
To unsubscribe from this group and stop receiving emails from it, send an email to cp2k+uns... at googlegroups.com<mailto:cp2k+uns... at googlegroups.com>.
To view this discussion on the web visit https://groups.google.com/d/msgid/cp2k/8432682b-63da-4365-ac25-e53733f7e262n%40googlegroups.com<https://groups.google.com/d/msgid/cp2k/8432682b-63da-4365-ac25-e53733f7e262n%40googlegroups.com?utm_medium=email&utm_source=footer>.

--
You received this message because you are subscribed to the Google Groups "cp2k" group.
To unsubscribe from this group and stop receiving emails from it, send an email to cp2k+unsubscribe at googlegroups.com<mailto:cp2k+unsubscribe at googlegroups.com>.
To view this discussion on the web visit https://groups.google.com/d/msgid/cp2k/97f8688a-52b4-47f2-98cb-6733be1a2a9cn%40googlegroups.com<https://groups.google.com/d/msgid/cp2k/97f8688a-52b4-47f2-98cb-6733be1a2a9cn%40googlegroups.com?utm_medium=email&utm_source=footer>.

-- 
You received this message because you are subscribed to the Google Groups "cp2k" group.
To unsubscribe from this group and stop receiving emails from it, send an email to cp2k+unsubscribe at googlegroups.com.
To view this discussion on the web visit https://groups.google.com/d/msgid/cp2k/ZR0P278MB07594DD22D0BCBA7F5FA9D699FD7A%40ZR0P278MB0759.CHEP278.PROD.OUTLOOK.COM.