Car-Parrinello Molecular Dynamics on excited state surfaces

TL;DR

This paper introduces a linear-scaling ab initio molecular dynamics method for excited electronic states using the RPA, enabling efficient simulation of excited state dynamics with accurate results.

Contribution

It develops a novel dynamical variational approach to RPA-based excited state molecular dynamics, reducing computational cost and complexity.

Findings

Exact agreement with analytical results on a two-level system

Significant reduction in computational effort compared to traditional methods

Successful modeling of excited state dynamics in a polyene lattice

Abstract

This paper describes a method to do ab initio molecular dynamics in electronically excited systems within the random phase approximation (RPA). Using a dynamical variational treatment of the RPA frequency, which corresponds to the electronic excitation energy of the system, we derive coupled equations of motion for the RPA amplitudes, the single particle orbitals, and the nuclear coordinates. These equations scale linearly with basis size and can be implemented with only a single holonomic constraint. Test calculations on a model two level system give exact agreement with analytical results. Furthermore, we examined the computational efficiency of the method by modeling the excited state dynamics of a one-dimensional polyene lattice. Our results indicate that the present method offers a considerable decrease in computational effort over a straight-forward configuration interaction (singles) plus gradient calculation performed at each nuclear configuration.