I want to do casscf calculation on porphyrin molecule with Fe as central metal ion at +3 charge. Before starting the casscf, I wish to start with general relaxation to get used with ORCA.
!cam-b3lyp def2-tzvp opt
%PAL NPROCS 32 END
* xyz 1 2
The above was my input header.
I have a query here, I used +3 charge of Fe and hence the total charge of the system is 1.
I used a low spin multiplicity 2.
For the CASSCF calculation for the same molecule, the CHARGE should be mentioned as +3 (charge of TM) or +1 (Charge of the system)?
As you are taking the complete system again for CASSCF calculations, so the same charge and multiplicity should be taken.
Thanks.
Can you suggest some information on nroot block in orca input??
Nroots is the number of CSFs(Configuration state functions) corresponding to a particular CAS space and multiplicity. For eg for Fe(3+)i.e. d5 conf, the minimal space with be (5,5) and for 2 multiplicity, there will be many states (exact number will be printed in the output). So, you can give for eg 10 and in the output you will see the total number of CSFs.
Then from there, you can run calculation including all CSFs and then from the output, choose the significant number of roots which are important.
For details, you can see my preprint on my RG account
In case of any doubt, feel free to ask me again.
Hi Rishu
Thank you so much for the clarification. I will get back after this trial.