A Coupled-Trajectory Strategy for Decoherence, Frustrated Hops and Internal Consistency in Surface Hopping

In this work, we
discuss decoherence, frustrated hops and internal
consistency in surface-hopping-based methodologies. We demonstrate
that moving away from an independent-trajectory picture is the strategy
which allows us to propose a robust and reliable surface-hopping scheme.
Based on the exact factorization and on the idea of coupled trajectories,
we consider the swarm of trajectories, that mimics the nuclear dynamics
in nonadiabatic processes, as a unique entity. In this way, imposing
energy conservation of the swarm and allowing the trajectories to
share energy when hops occur clearly indicates the route toward a
new surface hopping scheme. Encouraging results are reported, in terms
of electronic and vibrational time-dependent properties on the photodynamics
of fulvene and 4-(dimethyloamino)benzonitrile, modeled with full-dimensional
linear vibronic coupling Hamiltonians.