Valence Bond Wave-Function-Based Automatic Diabatization Approach

In this work, an automatic diabatization approach based on valence-bond (VB) wave functions, called VBADA, is proposed. Compared with the original VB based diabatization implementation [Zhang, Y.; et al. J. Phys. Chem. Lett. 2020, 11, 5295-5301; Zhang, Y.; et al. J. Phys. Chem. Lett. 2021, 12, 1885-1892], VBADA introduces two critical advancements: (1) the improved framework enables rigorous treatment of three-state diabatization, and (2) it relies on VB adiabatic wave functions rather than explicit Hamiltonian matrix operations. These are achieved by a novel criterion, which maximizes both the diversity of adiabatic VB wave functions and the trace of the adiabatic-to-diabatic (ATD) transformation matrix. The diabatic representations of two prototype hydrogen atom transfer (HAT) reactions, including Na + H₂ → NaH + H and H + HCl → Cl + H₂, is studied by employing VBADA. The computational results demonstrate that VBADA enables rigorous construction of three-state diabatic state, with benchmark validation showing exact numerical equivalence to conventional VB based diabatization implementation in two-state systems.