Transition metal systems and radical species pose a unique challenge in quantum chemistry due to the near-degeneracy of various electronic states, often defying description by a single electronic configuration. Multiconfigurational treatments, such as the complete active space self-consistent-field (CASSCF) method, are crucial for accurate results in these scenarios, particularly in systems with multiple interacting transition metals.

However, computational demands escalate dramatically when dealing with more than one metal center. In this talk, I will describe recent breakthroughs in overcoming the exponential scaling associated with the CASSCF method, enabling efficient treatment of complex systems with multiple transition metals.[1]

Moreover, multiconfigurational methods require careful user intervention in defining active spaces and orbital localization, precluding their use as black-box approaches, and limiting the availability of comprehensive datasets in the literature. To address this limitation, I will delve into our efforts to automate multireference methods for generating extensive datasets of excitation energies[2] and reactivity.[3] These datasets hold promise in training machine learning algorithms for enhanced predictive modeling in the challenging domain of strongly correlated systems. In the final part of the talk, I will outline our ongoing endeavor to automate the labeling of crucial features such as orbitals, which play a pivotal role in understanding chemical phenomena.

[1] V. Agarawal, D. King, M. R. Hermes, and L. Gagliardi Automatic State Interaction with Large Localized Active Spaces for Multimetallic Systems, submitted 2024

[2] D. S. King, D. G. Truhlar, and L. Gagliardi, Variational Active Space Selection with Multiconfiguration Pair-Density Functional Theory, J. Chem. Theory Comput. 2023, 19, 8118–8128

[3] J. J. Wardzala, D. S. King, L. Ogunfowora, B. Savoie, and L. Gagliardi Organic Reactivity Made Easy and Accurate with Automated Multireference Calculations, ACS Cent. Sci., 10.1021/acscentsci.3c01559 2024