Subject: Fenske-Hall methods

From: [email-masked]
Date: Tue, 14 Dec 1993 08:59:42 -0600 (CST)

Hi,

	The Fenske-Hall method is perhaps closest in spirit to Extended
Huckel.  Given our interests its biggest advantage is its applicability
to transition metal complexes.  Classic refs. are given below.  

	MB Hall, RF Fenske Inorg. Chem. 1972, 11, 768.
	BE Bursten, RF Fenske J. Chem. Phys. 1977, 67, 3138.  
	BE Bursten, RJ Jensen, RF Fenske J. Chem. Phys. 1978, 68, 3320.

	On the applications side, there is in addition to the work of
Hall and Bursten, really nice work by Lichtenberger on correlating photo-
electron spectral data with Fenske-Hall calculations.  I also recall seeing 
some work out of Cotton's group on the study of metal-metal bonded systems in
which Fenske-Hall calculations were integrated into the experimental analysis.

     Another big advantage to Fenske-Hall, in my opinion, is that like 
Extended Huckel it is SIMPLE and thus easily intepretable.  This makes it great
as an introduction to comp chem for undegrads and grad students.  The program
also has Z-matrix input, which may confound students the first time they 
see it, but once they get the hang of it, it beats calculating Cartesians
by hand.  In our introductory graduate class in structure and bonding at
Memphis State we have found it to be quite popular in the computational
exercises.  Given my bent, one of the nice things is that the students can also
gain exposure to computational inorganic chemistry, and thus makes a fine 
follow-on to simple Huckel methods.

	On the negative side, I would imagine that like Extended Huckel
methods there is the likelihood that calculating geometries is probably
going to be difficult.  As Hoffmann's work with EHT shows, if some
geometry is determined by a symmetry argument a simple approach is quite
informative; there is no reason to think that Fenske-Hall wouldn't also be 
useful in such a case.  A series of test calculations where there is some
corroborative experimental data would be well advised.  We have not done any 
prediction of geometries with FH, and if anybody on the net has any data on 
this I would be interested in hearing about it.

	On the research side, we have found that the method is quite
good at reproducing the composition of molecular orbitals (when compared
to our effective core potential calculations).  We have just finished 
a collaborative project with Jim Mayer at Washington and found the 
Fenske-Hall to be a useful adjunct to more sophisticated ECP calculations.
One particularly neat feature is the ability to decompose MOs from an 
AO basis to a fragment MO basis.  In fact, we would run Fenske-Hall calcs using
the fragment MO analysis on geometries optimized using our regular effective 
core potential methods in order to help guide us in analysis of the ECP wave-
functions. This feature is really useful when looking at organometallic 
complexes of the transition metals (as compared to traditional Werner-type 
complexes) since organometallics tend to show more delocalization of the
frontier MOs over the metals and ligands the bonding picture.

	Hope this helps.

					Sincerely,

					Tom Cundari
					Dept. of Chemistry
					Computational Inorganic Chemistry Lab
					Memphis State University
					Memphis, TN 38152
					phone: 901-678-2629
					fax: 901-678-3447

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From: "Dr. Paul Edwards" <[email-masked]>
Date: Tue, 14 Dec 1993 11:18:47 -0400 (EDT)

Is Fenske-Hall software available from an ftp site?

Paul Edwards
Edinboro University of PA
[email-masked]