# A grid-based Ehrenfest model to study electron-nuclear processes

## TL;DR

This paper introduces a grid-based Ehrenfest model for electron-nuclear processes that simplifies the computational complexity of simulating diatomic molecules by combining quantum and semi-classical dynamics.

## Contribution

The work presents a novel application of the Ehrenfest approach to treat nuclear motion in electron-nuclear systems, enabling scalable simulations with multiple nuclear degrees of freedom.

## Key findings

- Ehrenfest model shows good agreement with fully quantum results for H₂⁺.
- The approach is computationally efficient and easily extendable to more nuclear degrees of freedom.
- Demonstrates potential for modeling complex electron-nuclear interactions in molecules.

## Abstract

The two-dimensional electron-nuclear Schr\"odinger equation using soft-core Coulomb potentials has been a cornerstone for modeling and predicting the behavior of one-active-electron diatomic molecules, particularly for processes where both bound and continuum states are important. The model, however, is computationally expensive to extend to more electron or nuclear coordinates. Here we propose to use the Ehrenfest approach to treat the nuclear motion, while the electronic motion is still solved by quantum propagation on a grid. In this work we present results for a one-dimensional treatment of H$_2^+$, where the quantum and semi-classical dynamics can be directly compared, showing remarkably good agreement for a variety of situations. The advantage of the Ehrenfest approach is that it can be easily extended to treat as many nuclear degrees of freedom as needed.