class Coulomb : public feasst::ModelTwoBody
Compute energy between two point charges, \(q_i\) and \(q_j\) with a plain Coulomb potential.
\(U = q_i q_j \chi/r\)
where \(r\) is the separation distance, and \(\chi\) is the charge conversion factor assuming the following units:
Avoid singularity by returning a large, positive number when \(r\) is near zero.