Hybrid quantum trajectory approach for low temperature reactive processes in condensed phase – HYTRAJ

Combination of a formalism based on quantum trajectories and a formalism based on classical Hamiltonian equations. Extension to non-adiabatic processes by means of the exact factorization formalism.
«Exact« quantum method based on the Smolyak representation and absorbing potentials for medium size systems.

Formulation of the quantum trajectory method for stationary processes along a curvilinear reaction path (implementation of quantum potential terms from the metric tensor)
Application of the time-dependent formulation to model systems of adiabatic reactive processes (a single potential surface). First applications to non-adiabatic systems (Tully models).
Development of an all-quantum approach using Smolyak representations for chemical reactivity (used to validate the methodological developments proposed in this project).

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Application to complex molecular processes in the gas phase and to processes taking place on surfaces at low temperature.

2 articles in preparation

One of the present challenges of gas-phase reaction dynamics theory is to extend its capability to more complex (condensed phase) molecular systems. In this project, we explore a new and unconventional reaction dynamics approach based on quantum trajectories. Contrary to their classical counterparts, quantum trajectories are able to exactly capture quantum dynamical effects---tunneling, in particular. In one-dimensional cases, the quantum trajectory method has shown unprecedented numerical performance, especially at ultra-low temperatures, where quantum effects are of paramount importance. In large systems, quantum dynamical effects are often limited to one degree of freedom (the reaction path, usually), while the rest of the degrees of freedom behave classically. Making full use of this fact, we build a quantum-classical reaction dynamics method, \textit{entirely based on trajectories}. Here, we propose to use this novel approach to tackle reactions of complex systems with quantum effects, in particular at low temperatures where exact molecular collisions dynamics are notoriously difficult to simulate.