Author Topic: comparison of mp2 energies of gaussian and turbomole  (Read 12121 times)

adichhikara

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comparison of mp2 energies of gaussian and turbomole
« on: February 05, 2009, 11:27:16 PM »
Hello,

I am trying to compare the absolute MP2 energies between Gaussian 03 and Turbomole V5-9-1. I am also comparing the RI-MP2 energies of Turbomole with the MP2 Gaussian 03 energies.

I am doing a frozen core calculation with an aug-cc-pVDZ basis set (with the default5d/7f orbitals) in both Gaussian and Turbomole. The HF energies are the same between G03 and TM. However, the MP2 correlation energies are different. The RI-MP2 energies in Turbomole differ by around 0.5-1 kJ/mol while the MP2 energies differ by around 100 kJ/mol.

Do you have any ideas why this might be the case?

thanks,
Adi
« Last Edit: February 09, 2009, 07:49:01 PM by adichhikara »

antti_karttunen

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Re: comparison of mp2 energies of gaussian and turbomole
« Reply #1 on: February 06, 2009, 09:03:37 AM »
Hello,

Have you checked that the same number of core orbitals has been frozen in Gaussian and Turbomole calculations? The default "freezing" scheme in Gaussian is a bit different from the scheme used by define. Furthermore, did you really run RI-MP2 calculations in Gaussian03? RI-MP2 calcualtions with Gaussian03 should not be possible, at least according to the manual (the density fitting scheme in Gaussian03 can only be used for pure DFT, and according to my small test calculations their scheme differs from the RI-DFT used in Turbomole).

Regards,
Antti

adichhikara

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Re: comparison of mp2 energies of gaussian and turbomole
« Reply #2 on: February 09, 2009, 07:53:51 PM »
Hi Antti,

Thanks a lot for your suggestions. I did check to see if the core orbitals were the problem by doing a "full" MP2 calculation without any frozen orbitals. The problem was solved.

Sorry about the confusing post  :). I was comparing the RI-MP2 energies of Turbomole with the MP2 energies of Gaussian.

Does anybody know how to use the Gaussian default for the frozen orbitals in Turbomole? I think the default in Gaussian involves freezing all inner shell electrons.

thanks,
Adi
« Last Edit: February 09, 2009, 11:51:06 PM by adichhikara »

ubelix

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Re: comparison of mp2 energies of gaussian and turbomole
« Reply #3 on: February 10, 2009, 09:02:15 AM »
Hi Adi

I think you just have to enter "freeze" and then choose "exp" in the mp2prep script. This should give you the correct frozen orbitals...

Regards,
Andreas

adichhikara

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Re: comparison of mp2 energies of gaussian and turbomole
« Reply #4 on: February 18, 2009, 06:21:16 PM »
Hi Andreas,

Thanks for your reply. I'm using the jobbsee script for my calculations. Even when I explicitly set the freeze to "exp" in the control file like you suggested, the program still runs a "full" MP2 calculations. On the other hand, the reason the Ri-MP2 calculations were so close was that the RI-MP2 calculations had their core orbitals frozen by default without me having to specify anything.

Does anybody know of any other way to freeze orbitals for the jobbsee script?

Cheers,
Adi

christof.haettig

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Re: comparison of mp2 energies of gaussian and turbomole
« Reply #5 on: May 27, 2009, 11:51:14 AM »
Hi,

let me clarify a few things:

1) The mp2prep script doesn't  provide support for the frozen core option (mainly because the mpgrad program for which is meant only supports the frozen orbitals in energy but not in gradient calculations.

2.) The rimp2prep program is outdated and only kept for backward compatibility. Its functionality has been included in the mp2 submenu of define. For freezing orbitals rimp2prep and define offer the same options (and use actually the sameroutines).

3.) If you enter the freeze submenu in rimp2prep or in define (there it is available in the mp2 and cc2 menus), the program
     will by default freeze all occupied orbitals with orbital energies below 3.0 hartree, i.e. the 1s orbitals for Be and atoms beyond Be
     and  the 1s2s2p orbitals for Mg and atoms beyond Mg. For Atoms beyond Ar the automatic selection of core orbitals become more
     difficult (any suggestions are welcome!) and it recommended to check if the orbitals picked by the program are what one wants and
     if there is at all a clear seperation between the core and valence shells.

4) The jobbsse implementation in version 5.9 and 5.9.1 had problems with the frozen core options. They should be solved with the
     revised implementation that came with TURBOMOLE version 5.10.


Christof