Conditional wavefunction theory: a unified treatment of molecular structure and nonadiabatic dynamics

TL;DR

This paper introduces a conditional wavefunction theory that unifies the treatment of molecular structure and nonadiabatic dynamics, enabling efficient simulations of correlated electron-ion systems in both equilibrium and nonequilibrium states.

Contribution

It develops a variational wavefunction ansatz based on conditional wavefunction slices and extends it to time-dependent scenarios, addressing complex molecular processes.

Findings

Accurately describes hydrogen molecule structure and dynamics.

Successfully models strong-field ionization and laser-driven proton transfer.

Captures Berry phase effects at conical intersections.

Abstract

We demonstrate that a conditional wavefunction 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 wavefunction formally recasts the full interacting wavefunction of a closed system as a set of lower dimensional (conditional) coupled `slices'. We formulate a variational wavefunction ansatz based on a set of conditional wavefunction 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 wavefunctions, and address paradigmatic nonequilibrium processes including strong-field molecular ionization, laser driven proton transfer, and Berry phase effects induced by a conical intersection. This work paves the road for the application of conditional wavefunction theory in equilibrium and out of equilibrium ab-initio molecular simulations of finite and extended systems.