Abstract
We demonstrate that a conditional wave function theory enables a unified and efficient treatment of the equilibrium structure and nonadiabatic dynamics of correlated electron–ion systems. The conditional decomposition of the many-body wave function formally recasts the full interacting wave function of a closed system as a set of lower-dimensional (conditional) coupled “slices”. We formulate a variational wave function ansatz based on a set of conditional wave function slices and demonstrate its accuracy by determining the structural and time-dependent response properties of the hydrogen molecule. We then extend this approach to include time-dependent conditional wave functions and address paradigmatic nonequilibrium processes including strong-field molecular ionization, laser-driven proton transfer, and nuclear quantum effects induced by a conical intersection. This work paves the road for the application of conditional wave function theory in equilibrium and out-of-equilibrium ab initio molecular simulations of finite and extended systems.
Highlights
Emerging experimental capabilities in the precise manipulation of light and matter are opening up new possibilities to understand and exploit correlations and quantum effects that can be decisive in the functional properties of molecules and materials
We study dynamics around conical intersections (CIs) using a minimal generalization of the above Shin−Metiu model first proposed by Gross and co-workers[100] and extended further by Schaupp and Engel.[101]
We have introduced an exact mathematical framework that avoids the standard separation between electrons and nuclei and enables a unified treatment of molecular structure and nonadiabatic dynamics without relying on the construction and fit of Born−Oppenheimer potentialenergy surfaces and the explicit computation of nonadiabatic couplings
Summary
Emerging experimental capabilities in the precise manipulation of light and matter are opening up new possibilities to understand and exploit correlations and quantum effects that can be decisive in the functional properties of molecules and materials. This feature might be turned into an attractive playground from the computational point of view, as these quantities are usually demanding to obtain and fit from ab initio electronic structure calculations In this framework, one of the leading approximate methods to describe the coupled electron− nuclear dynamics for large systems is time-dependent density functional theory coupled to classical nuclear trajectories through the Ehrenfest method.[59] Due to its favorable systemsize scaling, the real-space picture Ehrenfest method has been successful for a great many applications, from capturing phenomena associated with vibronic coupling in complex molecular systems[60] and photodissociation dynamics in small molecules[61] to radiation damage in metals;[62] its efficiency allows calculations on large systems for even hundreds of femtoseconds.[63] It has been recently combined with the nuclearelectronic orbital method as a way to include quantum effects for selected nuclear degrees of freedom to study proton transfer processes in molecular excited states.[64].
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