Molcas Forum

azaichen

Member

Registered: 2023-04-03

Posts: 3

GUGA limitation?

Dear all,

I have a relative large molecule (32 atoms) and wish to calculate XAS spectra at the MRCI level of theory.

Unfortunately I have some troubles at GUGA step. Probably can somebody give me an advice about following points:

1) Is IOM = 55 - parameter in GUGA  an program restriction of electron pairs number? I try to include more inactive orbitals in the calculation due to the XAS-active core orbitals correlation, but my numbers become larger than 55 and I get always GUGA initialization error.

2) If I try to restrict the number of inactive orbitals with frozen of several core orbitals, I get yet one error of similar type that I have vertices number higher than 999.

I did MRCI calculations in other programs before and had no such troubles. Can be meaningful to increase the constants in program code or the calculation becomes too large anyway and better to delete and frozen more orbitals? What is maximal reasonable number of electrons and orbitals for GUGA and MRCI in OpenMolcas?

Best regards,
Alex

Last edited by azaichen (2023-08-11 22:15:58)