Subject: basis set for metal complexes (summary)

From: "Adel Abbas Ali Elazhary Sci. College" <[email-masked]>
Date: Mon, 14 Feb 2000 12:39:54 -0300 (GMT)

Dear ccl members:

About two weeks ago a I sent a question about basis set for metals. I 
received more requests to summerize than answers. The following are my
original question and the only answer I got.

Best regards,

Adel El-Azhary

=======================  original question   ======================  
 
Dear ccl members"
 
I am doing DFT calculations on metal complexes with organic molecules and
do not know what basis set should I use. Is there any study about basis
set effect on DFT calculated geometry or ir spectrum of metal complexes.
 
It might even help if someone suggest a test molecule for which its
vibrational spectrum (especially the bands corresponding to the metal
vibrations) are known.
 
Thanking you in advance.
 
Best regards,

=======================    only answer !  ============================

Calculating metal complexes there is not much choice of basis sets.
Using Gaussian, 6-311G is defined for 3d metals, but not for 4d and 5d.
4d and 5d are best calculated with pseudo potentials, which do take care
of relativistic effects. LanL2DZ is best known, but you can also choose
the Stuttgart Potentials (which are said to be implemented in G98, but
we tend to have problems with the internal basis sets and prefer to
specify in the input line. You can get basis sets input files on the net
(www.uni-stuttgart.de , than searching for the theochem group)

For 3d metals you have the choice of 6-311 and LanL2DZ or SDD - my
experience with copper complexes is, that 6-311 give slighty better
geometries, but do have convergence problems. 

Generally I do use mixed basis sets - e.g. 6-31(d) for the ligand and
LanL2DZ or 6-311G for the metal centre. 

Calculating frequencies - well, with pseudopotentials there is no direct
way to calculate them. They are calculating by searching systematically
the surface, which is a somewhat time-consuming procedure.

Best wishes

Achim  

Achim Lienke
PostDoctoral Research Fellow
Anorganisch Chemisches Institut
Universität Heidelberg
Im Neuenheimer Feld 270
D 69120 Heidelberg

Phone: ++ 49 6221 54 86 53
Fax: ++ 49 6221 54 66 17

===============================  end of the only answer ! =============