Subject: CCL:SUMMARY:elec.pot.:basisset depend.

From: Patrick Bultinck <[email-masked]>
Date: Thu, 30 Jun 1994 10:34:09 +0200 (MET DST)

Netters,

Please hereby find a summary of the answers C I received  on the
basis set dependancy of the charges fitted to the electrostatic
potential, and the electrostatic potential itself.

Hereby I wish to thank everybody who shared experiences, references,
opinions, and such...

ORIGINAL MESSAGE

Hello netters,

Does anybody have a reference, or rather an opinion or experience with
the basisset dependance of the electrostatic potential.

I would like to fit the charges to this potential since the n-dep. in
S^nPS^(1-n) in Mulliken (n=0) and Lowdin PA (n=0.5) scares me off a little.
That is why I would like to know how the basis set dep. of the elect. pot.
behaves compared with the MPA and LPA approaches...

Any comments much appreciated, (let me know if interested in a summary)

Patrick, University of Ghent, Belgium, [email-masked]

AND HERE ARE THE ANSWERS

Patrick:

I have done quite a few fits of partial atomic charges
to the electrostatic potential using the CHELPG program
as coded in G92. In my experience, once you are using
fairly large basis sets, the magnitudes of the partial charges decrease
regularly as the size of the basis set increases, both
at the HF and MP2 levels of calculation. On the other hand,
the Mulliken-derived charges tend to increase (but less uniformly)
in magnitude as basis set size increases.

For example, for oxygen in Si(OH)4 at the HF level:

        6-311G** basis                  6-311G(2d,2p) basis
Mulliken            CHELPG          Mulliken            CHELPG
- -0.711              -0.935           -0.881             -0.858

This trend is fairly typical of what I have seen. I don't know
how large a basis would be required to get convergence of this
charge?

Hope this is in some way useful. Good luck.

Brian Teppen
[email-masked]

Partrick,
        This is a very interesting question that you have asked, and I
would be interested in seeing a summary of the reponses that you recieve.
You might be interested in two references that I happen to have had laying
on my desk....

Jug, K.  Theoret. Chim. Acta 39,301-312 (1975)

Jug, K.  Theoret. Chim. Acta 31, 63-73 (1973)

These papers actually pertain more to charge distributions but there are
discussions (particularly in the first reference) to the influence of
basis sets on the calculation of electronic properties (multipole moments).
Thanks in advance for the summary and I hope this was somewhat helpful.

Kris

Kristopher Wise
Dept. of Chemistry and Biochemistry
University of Oklahoma
[email-masked]

You might find useful to have a look to
J.Comp.Chem., 11, 416 (1990)
JACS, 113, 5203 (1991).
and references therein

Good luck!

M. Orozco

Patrick,

You might find some information from

 F.J.Luque, F.Illas and M.Orozco, J.Comp.Chem., 11(1990)416;
 G.P.Ford and B. Wang, J.Comp.Chem., 14(1993)1101, 15(1994)200.

Roughly, Large basis sets generate a flat MEP with shallow wells
but large mep charges; minimal basis set gives a MEP with deeper
wells, smaller values in the far region and, therefore, smaller
mep charges.

Have a nice day,

Bingze Wang
IRBM, Rome, [email-masked]

Hello Patrick,

I've just published a paper about the basis
set dependence of ESP charges in a several
set dependence of ESP charges in a several
molecules. The dependence is much better
than the dependence of Mulliken charges.
It is much more convergent as the
basis set was increased. The paper
will appear in JCC in aug or sept
94.

Now I am about to leave for holydays
so if you are interested in more
detail be fast.

- ----------------------------------------------------------
Gabor I. Csonka                 Budapest University of Technology
Tel/FAX: (361) 18.12.177        Inorganic Chemistry Dept. Ch. Bldg
[email-masked]  H-1111, Bp. Szent Gellert ter 4
- ----------------------------------------------------------

        If it is true that the electron distribution is basis set-dependent,
it would follow that the ESP will be basis set-dependent.

        Much work has gone into the plotting of electron density maps and
density difference maps (The work of R. F. Bader is a good starting point.).
These maps clearly show basis-set dependence, rather dramatically for di- and
tri-atomics.

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Dear Computational Chemist:

        Molecular interactions occur during host-substrate docking, cluster,
and crystal formation - whenever molecules associate with one another.  The
energy and geometry of molecular association is determined by the force field.
As a component of the force field, an accurate set of net atomic charges is
needed.
        Reliable net atomic charges can be found by fitting the molecular
electric potential with program PDM93.  In addition to net atomic charges,
program  PDM93 also allows any combination of atomic dipoles/quadrupoles,
bond dipoles, as well as the addition of lone pair electron sites if required.
        A particularly useful feature of the program is the transparent way
in which fixed charges and charge dependency conditions are specified.  By
specififying appropriate charge dependencies (e.g., equal charges or equal
sums of charges), chemical intuition can assist to produce charges which are
transferable between related types of molecules.
        I append a brief description of program PDM93.

 -Don Williams

Program PDM93, Potential Derived Multipoles
The following is a brief description of this program.

        Molecules interact with each other via their electric potential.
PDM93 finds optimized net atomic charges and other site multipole
representations of the molecular electric potential based on a variety
of models.  The program is easy to use, flexible and powerful.  Results
are obtained in a single iteration and a complete error treatment is
made which includes estimated standard deviation and correlation of
variables.  The program is written in Fortran 77 and runs on Unix,
Vax, and other computers with F77 capability.

Program PDM93 has a unique combination of features:

o  general sites, e.g. united atoms, not necessarily at atomic locations
o  each site may have any combination of monopole, dipole, or quadrupole
o  bond dipole model is supported
o  restricted (along the bond direction) bond dipole model is supported
o  provision for site dipole vectors in sp2 or sp3 directions
o  selected fixed atomic charges
o  selected groups of atoms with fixed charge
o  atomic charge equalities or symmetry relations
o  rotational invariance of site charges
o  provision for optional foreshortening of X-H bonds
o  comparison with Mulliken charges and Mulliken electric potential
o  direct input from Gaussian-92 output file
o  generalized input from other quantum mechanics programs
o  automatic generation of electric potential grid points
o  provision for custom generation of grid points
o  on-line program manual
o  comprehensive examples are provided

        A review of potential-derived charges may be found in Reviews of
Computational Chemistry, Vol. II, pp. 219-271 (1991).  For further
information contact Dr. Donald E. Williams, Department of Chemistry,
University of Louisville, Louisville, Kentucky 40292, USA.

Tel:(502)852-5975 Fax:(502)852-8149 E-mail:[email-masked]
- -----------------------------------------------------------------------
Ordering information

Program package consisting of manuals, Fortran-77 source files,
and demonstration example files.........price reduced!.............$1,600
Discount price for academic institutions only........................$395

Choose the preferred method of shipment:

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- -------------------------------------------------------------------------

Patrick,
>
> Does anybody have a reference, or rather an opinion or experience with
> the basisset dependance of the electrostatic potential.
>
   This has been studied extensively. See:

Rodriguez et al. J. Comp. Chem. 14 (1993) 922.

Alkorta et al. J. Comp. Chem. 14 (1993) 530.

Alema'n et al. J. Comp. Chem. 14 (1993) 799.

Earlier work is referenced therein.

CJC

- --

Christopher J. Cramer
University of Minnesota
Department of Chemistry
207 Pleasant St. SE
Minneapolis, MN 55455-0431
(612) 624-0859
[email-masked]

    Hi Patrick,
>
> the basisset dependance of the electrostatic potential.
>
> I would like to fit the charges to this potential since the n-dep. in
> S^nPS^(1-n) in Mulliken (n=0) and Lowdin PA (n=0.5) scares me off a little.
> That is why I would like to know how the basis set dep. of the elect. pot.
> behaves compared with the MPA and LPA approaches...
>
    I've used CHELPG charges (G92, POP=(CHELPG,DIPOLE) and available in
   GAMESS as well) for a few projects as have others in my group.  I
  calculate a couple of basis sets for comparison and have seen changes,
  but only on a small scale (<0.07 e) as long as at least 6-31G(d) was
  used for the basis set.  Correlation seems to cause more changes
  (understandably), but the variations are no where near what you see
  with Mulliken.  I've had Mulliken charges which yield a dipole moment
  which is off by 1.2D!  CHELPG gets the dipole moment almost right
  even when you don't constrain it.

   Dan

Once such reference is:  Truhlar et al. in "Chemical Applications of Atomic
and Molecular Potentials", Politzer and Truhlar, eds. Plenum Press, NY
1981.  It's
old but still should be useful.  For basis set comparison of fits to
electrostatic potentials, see J.Comp. Chem. 8, 894 (1987).

Michelle M. Francl
Associate Professor of Chemistry
Bryn Mawr College
Bryn Mawr, PA 19010

Phone:  610-526-5108
FAX:  610-526-5086
Internet: [email-masked]

Hi there,

    I just came across your mail in CCL, and was wondering if you know
of any programs (public domain, or free) that would fit charges to
the electrostatic potential. I am in a need for such a program.
Thanks for any help that you might have to offer.

regards,
sundar

email [email-masked]