Excited state frequencies

Peter Knowles peterk at tc.bham.ac.uk
Wed May 2 08:19:30 BST 2001

You need to be aware that if you go with numerical differentiation,
then some of the finite displacements will lower the symmetry! This
means that it is difficult to write an input that will work for a
state that is not totally symmetric in the highest point group. The
work-around might be to work without symmetry (and then you could use
analytic 2nd derivatives, of course). The long-term solution is, of
course, analytic second derivatives including symmetry, but I would
not advise expecting that this will be available by any given date.

Theis Solling wrote at 14:29 on 1 May 2001:
 > Hi,
 > I have been trying to calculate the vibrational frequencies for acetone 
 > in the first B2 state (the geometry optimization converged) using an 
 > MCSCF wave function.  The manual (and indeed the out put too) say that
 > analytical second derivatives are not available for molecules with 
 > symmetry. I have been trying to use the CENTRAL and NUMERICAL options
 > but the program terminates with the =
 > message:
 > t  t  t  t  t  t  t
 >  =
 > *************************************************************************=
 > ********
 > *************************************************
 > When I try to run the calculation in C1 I run in to the root-fliping 
 > problem when I try to optimize the wave function for the second excited 
 > state and I cannot make the wave function converge.
 > Is it not possible to calculate MCSCF frequencies for anything else than
 > the ground state using MOLPRO? Any suggestions are welcomed
 > Cheers,
 > Theis Solling

Prof. Peter J. Knowles              
Email P.J.Knowles at bham.ac.uk  Phone +44-121-414-7472  Fax +44-121-414-7471
School of Chemistry, Univ. of Birmingham, Edgbaston, Birmingham, B15 2TT, UK.
WWW http://www.tc.bham.ac.uk/~peterk/

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