  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.
