The accuracy of reaction energy profiles calculated with
multi-configurational electronic structure methods and corrected by
multi-reference perturbation theory depends crucially on consistent active
orbital spaces selected along the reaction path. However, it has been
challenging in all but the simplest cases to choose molecular orbitals that can
be considered corresponding in different molecular structures. Here, we
demonstrate how active orbital spaces can be selected consistently along
reaction coordinates in a fully automatized way. The approach requires no
structure interpolation between reactants and products. Instead, it emerges
from a synergy of an orbital mapping ansatz [J. Chem. Phys. 2019, 150, 214106]
combined with our fully automated active space selection algorithm [J. Chem.
Theory Comput. 2016, 12, 1760]. The former we extend by including also virtual
orbitals rather than occupied ones only. We demonstrate our algorithm for the
potential energy profile of the homolytic carbon-carbon bond dissociation and
rotation around the double bond of 1-pentene in the electronic ground state.
However, our algorithm also applies to electronically excited Born-Oppenheimer
surfaces in a straightforward manner.Comment: 16 pages, 4 figure