title: Multireference state-specific Mukherjee's coupled cluster method with noniterative triexcitations.
abstract: We have formulated and implemented the multireference Mukherjee's coupled cluster method with connected singles, doubles, and perturbative triples [MR MkCCSD(T)] in the ACES II program package. Assessment of the new method has been performed on the first three electronic states of the oxygen molecule and on the automerization barrier of cyclobutadiene, where a comparison with other multireference CC treatments and with experimental data where available. The MR MkCCSD(T) method seems to be a promising candidate for an accurate, yet computationally tractable, treatment of systems where the static correlation plays an important role.
authors.affiliation: J. Heyrovský Institute of Physical Chemistry, v.v.i., Academy of Sciences of the Czech Republic, Dolejskova 3, 18223 Prague 8, Czech Republic.
authors.forename: Kiran
authors.initials: K
authors.lastname: Bhaskaran-Nair
authors.forename: Ondrej
authors.initials: O
authors.lastname: Demel
authors.forename: Jirí
authors.initials: J
authors.lastname: Pittner