[molpro-user] Computing higher roots in MRCI

Bernd Hartke hartke at phc.uni-kiel.de
Tue Apr 14 15:13:51 BST 2009

Gerald Knizia wrote:
> On Friday 10 April 2009 21:12, Jaffe, Richard L. (ARC-TSN) wrote:
>> I am interested in computing the 6th root of B2 symmetry in non-linear C3.
>> I can determine the first 6 roots, but I am trying to reduce computational
>> cost by obtaining accurate solution only for the 6th root.
> I don't know much about Molpros diagonalization routines, but from a purely 
> numerical standpoint I would guess that this is impossible. I'm not aware of 
> any matrix diagonalization algorithm that can calculate a specific 
> eigenvector without also calculating all lower (or all higher) ones.
you may want to check out things like "inverse iteration" or "filter
diagonalization" etc.

Best regards,
Bernd Hartke

Prof. Dr. Bernd Hartke             e-mail: hartke at phc.uni-kiel.de
Theoretical Chemistry              phone : +49-431-880-2753
Institute for Physical Chemistry   fax   : +49-431-880-1758
University of Kiel                 http://ravel.phc.uni-kiel.de/
Olshausenstrasse 40
24098 Kiel

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