Nonadiabatic Electron Nuclear Dynamics in TDDFT with Variational Quantum Nuclei

Electron-nuclear coupling in non-equilibrium dynamics plays a fundamental role in condensed matter physics, defining behavior from phase transitions to chemical reactions. Recently the dynamics of these processes have been able to be experimentally resolved in the time-domain, requiring a theoretical framework beyond the Born-Oppenheimer approximation to describe [1]. While approaches such as the multi-configuration time-dependent Hartree method have been successful at describing excited state dynamics of relatively small systems, the cost to precompute potential energy surfaces and non-adiabatic couplings becomes a significant bottleneck for larger systems. In this talk we develop a trajectory based variational ansatz which treats the electronic system at the level of time-dependent density functional theory, while simultaneously incorporating a nonadiabatic quantum mechanical description of the nuclei. This method is compared to multi-trajectory Ehrenfest dynamics in the resolution of nuclear effects within the optical spectrum of small molecules.

[1] Kiyoshi Ueda et al 2019 J. Phys. B: At. Mol. Opt. Phys. 52 171001