[molpro-user] FCI iteration termination: expansion set singular

Steven Fiedler sfiedler at csun.edu
Tue Jan 10 23:22:47 GMT 2012

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

More information about the Molpro-user mailing list