Molcas Forum

leo.c

Member

Registered: 2021-03-23

Posts: 5

Change of basis

Hello Molcas users,
I was wondering if it was possible to restart a calculation from a previously converged set of orbitals (RASSCF) but with a different basis set. I have been successfully using the EXPBAS procedure with ANO basis sets to restart RASSCF from a previous calculation using a minimal basis, but doing so with correlation consistent basis (cc-pwCVTZ) results in a failure. If I restart a job from the .RasOrb file or the .GvOrb generated by Luscus with my new basis set (after running gateway/seward), I encounter an error saying there is a basis mismatch. Is it possible to transform the orbitals in the new basis set or alternatively am I missing something while using expbas with correlation-consistent basis (as I saw somewhere that this should be possible with any generally contracted basis set).

Thank you

Ignacio

Administrator

From: Uppsala

Registered: 2015-11-03

Posts: 1,079

Re: Change of basis

It should be possible when the new basis is a superset of the old one, and Molcas knows about it. I'm not sure the cc basis sets are properly configured for this.

Otherwise, transforming/projecting the orbitals from one basis to another is theoretically possible but not implemented in (Open)Molcas as far as I'm aware. There are probably tools to do it, but they'll probably not work with Molcas formats.

valera

Administrator

Registered: 2015-11-03

Posts: 127

Re: Change of basis

leo.c, EXPBAS works only with ANO-types of the basis sets. As Ignacio mentioned, it is theoretically possible, but not implemented.
And I think I know why - Molcas in many respects is tuned for use of ANO- type basis sets.

leo.c

Member

Registered: 2021-03-23

Posts: 5

Re: Change of basis

Thanks for your replies.
I'll stick to using a ROHF starting point for calculations with basis sets other than ANO.

Last edited by leo.c (2021-03-24 18:51:40)