Morse Potential Potential Problem?

Either I am missing something really stupid or something is wrong. I am trying to run some basic tests of the radial distribution functions of the morse potential. I used the default parameters from the lammps manual, which as I understand them is a D0 of 100kcal/mol, Alpha of 2 Å-1, and a Rmin of 1.5 Angstrsoms. Given a simulation at 300 K I would expect a maxima at 1.5-1.6 Å. However the simulation produces a first maxima of 1.15Å.

Any ideas would be appreciated.


The doc page actually refers to r0, but I think it is the energy minimum. The RDF depends on the density. If you squeeze them hard enough, they will move closer together than Rmin. Trying lowering the density.