Multireference coupled cluster study of the oxyallyl diradical

Abstrakt

Adiabatic singlet-triplet gap of the oxyallyl diradical has been studied by multireference Brillouin-Wigner and Mukherjee's coupled cluster methods (BWCC and MkCC). The results demonstrate the necessity to include connected triples excitations, as well as employing a size-extensive MRCC method.

The best result, calculated at the MkCCSD(T-u)/cc-pVQZ level, is in an excellent agreement with both experiment and recent spin-flip EOMCCSD(dT) calculations.

Klíčová slova

• multireference methods
• coupled cluster
• Brillouin-Wogner