Local diabatic representation of conical intersection quantum dynamics

Conical intersections are ubiquitous in polyatomic molecules and responsible for a wide range of phenomena in chemistry and physics. We introduce and implement a local diabatic representation for the correlated electron-nuclear dynamics around conical intersections. It employs the adiabatic electronic states but avoids the singularity of nonadiabatic couplings, and is robust to different gauge choices of the electronic wavefunction phases. Illustrated by a two-dimensional conical intersection model, this representation captures nonadiabatic transitions, electronic coherence, and geometric phase.