Assessment of Multireference Perturbation Methods for Chemical Reaction Barrier Heights

A few flavors of multireference perturbation
theory, two variants
of the n-electron valence state perturbation theory
and two of the complete active space perturbation theory, are here
tested for the calculation of barrier heights for the set of chemical
reactions included in the DBH24/08 database, for which very accurate
values are available. The comparison of the results obtained with
these approaches with those already published for other theoretical
models indicates that multireference perturbation theory is a valuable
tool for the description of a chemical reaction. Moreover, limiting
the comparison to the perturbation theory approaches, one observes
that the bad behavior found for single reference methods (such as
Møller–Plesset to second and fourth order in the energy)
is markedly improved upon moving to the multireference generalizations.