Subject: lanthanide chemistry

From: [email-masked]
Date: Tue, 31 Aug 1993 18:50:46 -0600 (CST)

Hi,

	The latest version of GAMESS from Mark Gordon and the Iowa State
group has the lanthanide ECPs and valence basis sets developed by myself
and Walt Stevens (JCP 1993, 98, 5555) built in.  For now, they are limited to
single-point energy runs, but work with any wavefunction. 
	Our initial results at Memphis State for predicting the structure of 
the simplest lanthanide trihalides are excellent (i.e., reproduction of
bond lengths to within 1-3%).  We run into the usual problem for d- and
f-block chemistry with regards to energetics, i.e. there is a limited
exptl. data base to compare with, so the jury must remain out on that one
for now.
	It is my understanding that the Ross-Pitzer-Ermler team is in the
last phases of developing and testing ECPs and valence basis sets for 
the lanthanides.  Dolg, Preuss and Stoll have developed lanthanide 
effective core potentials with a variety of core sizes.  So there are
a few options on the ab-initio side.
	As far as semi-empirical approaches, the only one I am aware of
is the INDO appraoch derived by Mike Zerner, Notker Rosch and co.   
	One application of computational methods to lanthanides that we are
very excited about is the use of molecular mechanics.  I commend to the
attention of anyone interested in such an approach to lanthanide chemistry
the paper by Ben Hay (IC, 1991, 30, 2876).  We have implemented Ben's
paramters into Chem3D+ on a Quadra 800 and in the space of an hour we can
optimize the structure of a good sized lanthanide complex, include a dozen or 
so simulated annealing cycles.  The coupling of the Chem 3D+ GUI with the 
MM2 force field eases the analysis and treatment of high coordination number 
lanthanide complexes.

				Tom Cundari
				Assistant Professor
				Department of Chemistry
				Memphis State University
				Memphis, TN 38152
				phone: 901-678-2629
				fax: 901-678-3447