[molpro-user] FCI iteration termination: expansion set singular
tania at tiger.chem.uw.edu.pl
Wed Jan 11 11:58:50 GMT 2012
If the basis set is large and your distance is small, this can be a numerical
linear dependency. You can try tighter thresholds for integrals etc.
(gthresh,twoint=1.e-25) and see if this helps.
On Tue, 10 Jan 2012, Steven Fiedler wrote:
> Dear Molpro users:
> I am conducting a series of FCI calculations of multiple states of the He2*
> dimer at various internuclear separation distances with a large basis set.
> Calculations of small separation distances (< 2 bohr) terminate after a
> number of FCI iterations with the following error: "expansion set singular".
> Prior to this error, the lowest root appears to be converging rapidly to
> minus infinity.
> Insight or advisement would be appreciated.
> Steven Fiedler
> Department of Chemistry and Biochemistry
> California State University, Northridge
> Molpro-user mailing list
> Molpro-user at molpro.net
Dr. Tatiana Korona http://tiger.chem.uw.edu.pl/staff/tania/index.html
Quantum Chemistry Laboratory
University of Warsaw
Pasteura 1, PL-02-093 Warsaw, POLAND
`The man who makes no mistakes does not usually make anything.'
Edward John Phelps (1822-1900)
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