We tested our program using one string of beads to model one particle, the
electron in a hydrogen atom.
Hydrogen is tricky, though: computers are stupid and will crash the
electron into the nucleus since the Coulomb
potential goes to negative
infinity at the nucleus.
Instead of the Coulomb potential, we use the Yukawa potential, developed by Muser and Berne
for this use in 1997. As you can see, it is just like the Coulomb
potential until you get close to the origin, and then it drops off less
steeply and goes to some finite value.
It turns out that the Yukawa potential is a very accurate way to model
the Coulomb potential, which governs both hydrogen and positronium
behavior.