PC GAMESS/Firefly-related discussion club

sanya
sanya@photonics.ru

Yes. $CONTRL SCFTYP=UHF MPLEVL=2 MULT=1 $END

>Most of the published studies from journals make use of MP2 for close shell and UMP2 for its corresponding radical cation.

Restricted and unrestricted calculations are of different accuracy levels. Suffice it to say that in unrestricted calculations you use twice as many basis functions as in restricted calculations. It is not the only reason why you should use same levels for singlet and doublet, but the first one that comes to my mind.

>I have also read that using ROMP2 for doublet also give good results compared to UMP2 due to spin contamination.

Using ROMP2 for doublet and MP2 for singlet is OK. It is even better than UMP2 for both.