Diabatization around Conical Intersections with a New Phase-Corrected Valence-Bond-Based Compression Approach

In the present work, valence-bond-based compression approach for diabatization (VBCAD), previously presented in literature [J. Phys. Chem. Lett. 2020, 11, 5295–5301] case of avoided crossings, is extended to more general situation conical intersections and their vicinity. A pointwise phase-correction scheme diabatic states proposed, based on explicit use peculiarities nonorthogonality ab initio valence bond (VB) theory. Rather than fitting or propagating nonadiabatic couplings, it allows us determine phase consistently automatically at each geometry point. Moreover, shown that undetermination degenerate around a intersection can be fixed naturally from straightforward classical VB picture. These are illustrated with two prototypical symmetry-induced (Jahn–Teller) models.