Bringing coupled‑cluster theory to the strong-correlation frontier

Accurate prediction of molecular electronic energies is essential yet remains challenging for strongly correlated systems, where conventional coupled-cluster (CC) methods break down. Here we present a generalized valence bond-based block-correlated coupled‑cluster (GVB-BCCC) framework to overcome this limitation. In contrast to standard CC approaches built upon a single-determinant reference, our method employs a multi‑determinantal GVB reference paired with a cluster operator that consistently captures both static and dynamic electron correlation effects, while retaining computational efficiency comparable to single-reference CC theory. With its O ( N ⁷) scaling, GVB‑BCCC delivers chemical accuracy for global potential energy surfaces, reaction barriers, and singlet‑triplet gaps across diverse biradicals and transition-metal complexes. GVB-BCCC thereby enables routine, black-box quantum-chemical predictions for a wide variety of strongly correlated systems, ranging from transition-metal catalysts and organic radicals to functional molecular materials.