Subject: Summary: atomic symmetry in G94

From: [email-masked] (Georg Schreckenbach)
Date: Wed, 26 Nov 1997 15:30:43 -0700

Dear CCL readers,

here is my summary on the atomic symmetry in G94 and related issues.

I got a number of interesting replies that are listed below. Eventually,
I solved my problem by simply refraining from using very diffuse basis
functions on Fe -- the Fe+ case should, indeed, give 5 equivalent d
orbitals as it has a half-filled shell. The suggestion of first running a
lower basis set to build the guess (Brian Teppen) is also useful,
and I have done just that in a number of other cases. Finally, I have
also posted this summary at

http://www.t12.lanl.gov/~schrecke/research.DIR/CCL_G94Atoms.html

Thanx again to everyone who took the time to reply!

A Happy Thanksgiving to all of us in America and elsewhere!

Best regards, Georg

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Original question:

I am trying to run a few atoms or ions (e.g., Fe_+) in Gaussian 94,
restricted open shell. My incentive is to compare orbital energies
as they come out of different methods and / or basis sets.
  Now, when I run such an atom, the program turns off symmetry.
This would not bother me too much if the subsequent SCF had
not mixed up states. However, it does so, and I do not get, for
instance, 5 degenerate d orbitals of the same energy. I tried to
enforce some symmetry by placing other nuclei into symmetric
positions far away but then I run into SCF convergence problems.

Any advice or tricks?

Best regards, Georg

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Date: Fri, 21 Nov 1997 11:47:35 -0600
From: "Vitaly A. Rassolov" <[email-masked]>

Dear Georg,

As far as I know, there is no way to solve your problem within
Gaussian package. This was the original philosophy of
Gaussian creators: stay away from symmetry in favor of the lower
 energy. Gaussian is an extreme case, but I don't know any other
molecular program which can enforce proper atomic symmetry
(although they usually don't mix the symmetry they have during
SCF iterations).

[Comment of GS: ADF does allow the use of the full atomic
symmetry, or of any lower symmetry as desired.]

Fe+ is, of course, an exception with its half-filled d-shell. It
should be similar to Mn, which does give me five identical d
orbitals, even on the UHF level (since the lowest energy
configuration is symmetric). You only have to make sure you
converge to the true minimum by using "stable=opt" option.

[Comment of GS: I don't get the "stable=opt" option to work with
my restricted calculation, B3LYP in this case. An unresticted
calculation seems to give the proper five d orbitals, even
without the "stable" keyword.]

When I need proper atomic symmetry, I use ATOMSCF program
 by B. Ross & Co. from the 60's. If you find out how to force
Gaussian to give identical d orbitals for not spherically symmetric
atoms, please share your information on CCL. I know couple
other people who would like to know it.

Best wishes,

Vitaly Rassolov
Department of Chemistry tel. (847) 491-3423
Northwestern University
2145 Sheridan Rd.       [email-masked]
Evanston, IL 60208-3113

---------------------------------------------------
Date: Fri, 21 Nov 1997 21:06:27 -0800
From: "Ananikov V.P." <[email-masked]>

Dear Georg,

As I know, it is possible to use high symmetry groups for
single atoms/ions (up to d2h) only if the starting electron density
is symmetric. For Fe+ you should choose C1 group, otherwise
d electrons might be nonequivalent at the end of your calculations.

You can try MCSCF and C1 group for Fe+, it seems it works
with GAMESS(I am not sure ;-).
If you do not have GAMESS near at hand, let me know.

Of course, I am interesting in your summary.

Good luck!

Valentin.

Valentin P. Ananikov

NMR Laboratory
N.D. Zelinsky Institute of Organic Chemistry Leninsky Prospect 47
Moscow 117913, Russia

e-mail: [email-masked]
http://nmr1.ioc.ac.ru/Staff/AnanikovVP/
Fax     (7095) 1355328
Phone (7095) 9383536, (7095) 1359094

---------------------------------------------------
Date: Fri, 21 Nov 1997 20:37:58 +0100 (MET)
From: "Dr. Alexei Arbouznikov" <[email-masked]>

Dear Georg,

Unfortunately, if you use restricted Hartree-Fock within the Gaussian
program, you can not get the correct degeneracy of the open shells,
except for the simplest case of exactly half-filled open shells (try,
e.g., Mn++ ion - d5 configuration, and you will obtain 5 degenerate
d-orbitals). To get the correct degeneracy in some more complicated
configurations (non-half-filled one open shell or several open shells,
e.g., 3d and 4s with occupation numbers other than 1/2 for at least
one of them), you have to use GVB(0) option in the Gaussian, and
specify explicitely the vector coupling coefficients for the desired
state (the way to do it should be indicated in the G94 manual). Other
solution of this problem is using another ab initio programs with
well-elaborated ROHF techniques, such as, e.g., Monstergauss-92.

If you are interested in, please, ask some additional questions.

Best regards,

Dr. Alexei Arbouznikov

Ecole Nationale Superieure de Chimie,
Laboratoire de Materiaux Catalytiques et Catalyse en Chimie Organique, UMR
5618 CNRS-ENSCM - Prof. F.Fajula, 8, rue de l'Ecole Normale
34296 Montpellier, Cedex 5
FRANCE

Telephone: (33) 4-67-14-72-68
Fax: (33) 4-67-14-43-49
E-mail: [email-masked]

---------------------------------------------------
From: Anatoli Korkin <[email-masked]>
Date: Fri, 21 Nov 1997 14:13:28 -0700 (MST)
Georg,

Send me an input example to [email-masked] and I will check
it for you. I will be in Gainesville tomorrow. But it could be simply
that your orbitals are not populated equally, than you obviuosly
has lower symmetry than Oh.

(...)

Best wishes,

Anatoli Korkin

Anatoli Korkin Ph.D     [email-masked] !!! New !!!
Computational Chemist   [email-masked] still works,
but change it to the new one !!!

Tel: (602) 655-3171
Fax: (602) 655-2285

Predictive Engineering Lab      Semiconductor Products Sector
Arizona Technology      Motorola Inc., MD M350
Laboratories    2200 West Broadway Road
Mesa AZ 85202

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Date: Sat, 22 Nov 1997 12:31:26 -0800
From: "Ananikov V.P." <[email-masked]>
Subject: Re2: CCL:G:atomic symmetry in G94

Dear Georg,

A few additional comments concerning your request on Fe+.
The close question has been discussed in GAMESS-Users-List,
and here is one of the messages:
____________________________________________________________________________
Subject: Re: GU: Symmetry of atoms
Date: Mon, 17 Nov 1997 10:02:02 -0600 (CST)
From: [email-masked] (Kurt Glaesemann)
Reply-To: [email-masked]
To: [email-masked]

>When I want to perform some calculations on atoms (or monoatomic ions),
I wonder about the symmetry to choose. There are 2 input examples dealing
with atoms, and they both have the symmetry D2h. Is that a generally
acceptable choice? If not, what should the choice be based upon?
It's the higher albelian group. It will keep your x, y, and z pure. This of
course, assumes that the electron density easily symetric. If you do Fe+,
you have to choose group=c1 in $DRT and state average the sextet,
so that all d's are equivelent, otherwise they are inequivelent.
____________________________________________________________________________

best regards,
Valentin.

Valentin P. Ananikov

NMR Laboratory
N.D. Zelinsky Institute of Organic Chemistry Leninsky Prospect 47
Moscow 117913, Russia

e-mail: [email-masked]
http://nmr1.ioc.ac.ru/Staff/AnanikovVP/
Fax     (7095) 1355328
Phone (7095) 9383536, (7095) 1359094

---------------------------------------------------
Date: Mon, 24 Nov 1997 10:23:46 -0500
From: Brian Teppen <[email-masked]>

Hi, Georg:

I have done HF/DFT calculations on Fe complexes, and have
naturally suffered convergence problems. One trick that seems
to often work is to do an initial single-point calculation using
STO-3G. Give it many cycles (say, MaxCycle=200) because they
are cheap. Then, use the STO-3G wavefunction as the initial
guess for some Gaussian basis set. It might be worth a try.

Best wishes,

Brian J. Teppen [email-masked]
Advanced Analytical Center for Environmental Sciences
Savannah River Ecology Laboratory
University of Georgia
Drawer E
Aiken, SC 29802

phone:803-725-8157      fax:803-725-3309

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END OF SUMMARY

--
Dr. Georg Schreckenbach           Tel:     (USA)-505-667 7605
Theoretical Chemistry T-12        FAX:     (USA)-505-665 3909
M.S. B268, Los Alamos National      E-mail:  [email-masked]
Laboratory, Los Alamos, New Mexico, 87545, USA
Internet:    http://www.t12.lanl.gov/~schrecke/