[molpro-user] UCCSD(T) and RMP2

Rafal Bachorz rafal.bachorz at chemie.uni-karlsruhe.de
Mon Mar 13 12:47:10 GMT 2006

Dear Molpro Users,

When carrying out the CCSD/CCSD(T) (for the closed shell system of course) one 
gets in the output file the mp2 enery. On the other hand there is no this 
information in case of UCCSD/UCCSD(T) calculation. My question is how I can 
get mp2 energy of the open-shell system which is equivalent to the mp2 energy 
printed out during CCSD(T) calculation of the closed-shell one. 

For UCCSD(T) calculation I have been using 2002.6 linked 13 version of molpro, 
and to the best of my knowledge the ROHF reference is used for this purpose. 
I have found in the manual that there are the following methods implemented 
in molpro for open-shell cases:

ump2    !second-order Moeller-Plesset perturbation theory with UHF reference 
rmp2    !second-order Moeller-Plesset perturbation theory with RHF reference.
ci      !singles and doubles configuration interaction (using the MRCI 
rcisd   !spin-restricted singles and doubles configuration interaction
ucisd   !spin-unrestricted singles and doubles configuration interaction
rccsd   !partially spin adapted coupled cluster with singles and doubles
rccsd(t)!partially spin adapted coupled cluster with perturbative
        !of triples
uccsd   !spin-unrestricted coupled cluster with singles and doubles
uccsd(t)!spin-unrestricted coupled cluster with perturbative
        !treatment of triples

My guess is that I need to use the rmp2 keyword, am I right? 

Any help is appreciated very much.

Best regards, 
Rafal Bachorz.

Rafal A. Bachorz
Chair of Theoretical Chemistry
Institute of Physical Chemistry
University of Karlsruhe (TH)
D-76128 Karlsruhe, Germany
Email: rafal.bachorz at chemie.uni-karlsruhe.de
Telephone: +49-721-608 7269
Engesserstrasse 15, D-76131 Karlsruhe
Building 30.45 (Chemie-Turm III), Room 620

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