Subject: Transition Metals in Gaussian Summary

From: "Benjamin J. Moritz" <[email-masked]>
Date: Thu, 02 Nov 2000 09:37:35 -0700

I thank all who helped me in overcoming my problem with Gaussian 98 and 
transition metals basis sets.  I was able to overcome the problem with the 
GEN keyword and the LANL2DZ and am trying other basis as well. Below is a 
summary of the responses I received.

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If you are performing some calculations on heavy atoms you have to use
some pseudo-potential. You cannot simply use a basis set such as e.g.
6-311G**.
You can use the following statements (for example):
#B3LYP/GEN Opt Pseudo(SDD)
or
#B3LYP/GEN Opt Pseudo(Read)
In the first case G98 will use the Stuttgart pseudo-potential. The GEN
keyword specifies that you have to put, at the end of your input file, the
basis set for all atoms. I suggest you to have a look to the web site:
http://www.emsl.pnl.gov:2080/forms/basisform.html
In the second case you have to specify both the basis set (GEN) and the
pseudo-potentials.
I guess you can also have such a line command:
#B3LYP/6-31G Opt Pseudo(SDD)
In this case, the 6-31G will be used for light atoms. But you still have
to put the pseudo-potentials for heavy ones.
You can retrieve the well-formatted basis sets and pseudo potentials in
the web site I have just mentioned.
***************************************************************
For Hg (and most transition metals) you will need to use a basis set
modified with an electrostatic core potential (ECP) which basically removes
the core electrons from the atom and replaces them with an empirical
potential. G98 comes with the LANL2DZ basis and ECP built-in. If you want
to use this basis then set your input like the following:
#P RHF/GEN Pseudo=read
comments...
charge multiplicity
molecular specifications
C N 0
6-31+G(d')
****
Hg 0
LANL2DZ
****
Hg 0
LANL2DZ
The important parts are the Gen and Pseudo=read - this tells gaussian to
look at the end of the input file for the basis set (which can be different
for each atom) and the ECP. In the example above I used carbon and
nitrogen, you would put the element symbol for whatever atoms are in your
molecule there. Let me know if this works for you!
ATTACHMENT AT END OF FILE!

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LanL2DZ basis set should be enough as it goes up to atomic number 83 I
have used it for a number of transition metals already and had no
problems.
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According to the Basis Set Order Form, mercury is only available with the
following basis sets:
WTBS
SBKJC VDZ ECP
CRENBL ECP
CRENBS ECP
Stuttgart RLC ECP
Stuttgart RSC ECP
Ahlrichs Coulomb Fitting
http://www.emsl.pnl.gov:2080/forms/basisform.html
They can be used in Gaussian with the GEN keyword. I do not have any
experience with any of these basis sets.

**************************************************************
You've discovered one of the annoying things about calculations involving
elements past chlorine: not all basis sets have been "parameterized" for all
elements. Somewhere near the front of the G98 manual is a table of which
built-in basis sets are defined for which elements.
For your calculations on Hg compounds, your choices are to use one of the
built-in basis sets that is defined for that element, or to use gen and
pseudo=cards to read in a basis set and pseudopotential that is not built
into Gaussian.

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Benjamin J. Moritz                                       home (602) 453-9411
Dept. of Chemistry & Biochemistry                 work (480) 965-8509
Arizona State University                                Mailto:[email-masked]
P. O. Box 871604
Tempe, AZ  85287-1604
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