Subject: ab initio questions

From: Dale Braden <[email-masked]>
Date: Sat, 5 Oct 1996 15:40:34 -0700 (PDT)

Dear CCL,

I would like to post two questions about ab initio computations.

1)  The output of a frequency calculation normally includes the 
mass-weighted nuclear displacements for each normal mode, along with the 
reduced mass.  Does anyone know how to calculate the *absolute* nuclear 
displacements, given the kind of data available from a frequency 
calculation by, for example, Gaussian 94?

2) In looking through the literature on calculations for organometallic
complexes, I have noticed that polarization functions are often NOT added
to the basis set for the transition metal, although they are always added
to first-row atoms.  Furthermore, for anionic systems, diffuse functions
will be added only to the basis set used for the ligand atoms, but not to
that for the metal.  Now, perhaps calculations using such basis sets will
agree well with experiment, but wouldn't this be fortuitous, since the
basis set is unbalanced?  Do the readers agree with the above practice? 

I shall promptly summarize all responses.

Thank you,

Dale Braden
Department of Chemistry
University of Oregon
Eugene, OR 97402
[email-masked]