Corresponding Active Orbital Spaces along Chemical Reaction Paths

TL;DR

This paper presents an automated method for selecting consistent active orbital spaces along reaction paths, improving the accuracy of multi-configurational calculations without requiring structure interpolation.

Contribution

It introduces a fully automated algorithm combining Direct Orbital Selection and autoCAS for consistent active space selection along reaction coordinates.

Findings

Successfully applied to carbon-carbon bond dissociation in 1-pentene

Works for both ground and excited electronic states

Eliminates need for structure interpolation in active space selection

Abstract

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 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 automated way. The approach requires no structure interpolation between reactants and products. Instead, it emerges from a synergy of the Direct Orbital Selection orbital mapping ansatz combined with our fully automated active space selection algorithm autoCAS. 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.