Fenske-Hall methods

[CUNDARIT' at \`MSUVX1.MEMST.EDU]

 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