For open shell the following single-reference methods are implemented in MOLPRO:

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 program) 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 !treatment of triples uccsd !spin-unrestricted coupled cluster with singles and doubles uccsd(t)!spin-unrestricted coupled cluster with perturbative !treatment of triplesAgain, there are also explicitly correlated and local variants of many of these methods, see sections 18 and 17, respectively.

Note that all methods except `ump2` use spin-restricted Hartree-Fock (RHF) reference functions.
This is also the case for the `ucisd` and `uccsd` methods, in which the correlated
wavefunction may be slightly spin contaminated, even though the
RHF reference function is spin adapted.
`ump2` is not generally recommended,
since spin contamination can lead to large errors.

Core orbitals can be specified as for the closed-shell methods. The number of electrons and
occupations as well as the orbitals are taken from the most recent RHF calculation.
It is possible to modify these defaults using `occ`, `closed`, `wf`, or `orbital`
directives; see the MOLPRO reference manual for details.

The following is an example of a complete CCSD(T) calculation for O.

***,O2 print,basis,orbitals geometry={ !geometry specification, using z-matrix o1 o2,o1,r } r=2.2 bohr !bond distance basis=vtz !triple-zeta basis set {hf !invoke RHF program wf,16,4,2 !define wavefunction: 16 electrons, symmetry 4, triplet occ,3,1,1,,2,1,1 !number of occupied orbitals in each symmetry open,1.6,1.7} !define open shell orbitals rccsd(t) !perform partially spin adapted CCSD(T)

molpro@molpro.net 2018-08-16