Molcas Forum

timothe33

Member

Registered: 2022-04-25

Posts: 12

Issue Alter orbital in RASSCF

Dear Molcas users,

I am running a calculation on a lanthanide molecule with an ECP and in C2v symmetry using RASSCF. I have the following input:

&RASSCF
FILEorb
*LuF_ANO-TZ.ScfOrb
LuF_ANO-TZ_RAS_1_1_new5.RasOrb
*Alter= 1; 1 16 23
Spin = 1
Nactel = 8 2 2
Frozen = 10 5 2 5
RAS1 = 1 1 0 1
RAS2 = 4 2 1 2
RAS3 = 1 1 0 1
CIroot = 9 9 1
SYMMetry= 1

My issue is whatever I tried, I can not swap the last orbital in the active space for the A1 symmetry. I tried to use Alter for different orbitals, tried to manually change the orbital in .RasOrb file.

Any idea  how swap orbital 16?

Best,

Ignacio

Administrator

From: Uppsala

Registered: 2015-11-03

Posts: 1,085

Re: Issue Alter orbital in RASSCF

My guess is you indeed swap the orbital, but then during the orbital optimization, the orbital is rotated of the active space. This typically happens because there is no state (among the ones included in the state average) where the occupation of the orbital is significantly different from 2.0 or 0.0, and therefore there's a benefit (i.e., lower energy) if a different orbital is included in the active space.

You could try increasing the number of states in CIRoot (maybe first with CIOnly), or preventing unwanted rotations with SupSym.

timothe33

Member

Registered: 2022-04-25

Posts: 12

Re: Issue Alter orbital in RASSCF

Thank you Ignacio,

I will try it out to see if it helps

Best,