On Fri, 18 Feb 2011, N H wrote:
Well I'm not talking about the Born Oppenheimer approximation, which has nothing to to with my question!
OK, so I guess I did not understand your point. I'm sorry if this is the case. Maybe someone else in the list will provide a more specific answer.
Potential energy has a clear meaning in mechanics. If you put kinetic and potential together what you have is total or internal energy. It is terminology? Sure ... but I guess it is somehow misleading.
The potential energy (E_KS) has exactly the meaning you refer to anyway. It is the potential energy of your "atomic system", in the sense that, if you add to it the kinetic energy of the "atomic system" you get the total energy of the system. It seems that you are visualizing your system as formed by both nuclei and electrons, then the total kinetic energy would be, I admit, the sum of the kinetic energies of nuclei and electrons. But this is a non-standard partition as regards classical Molecular Dynamics simulations. But I insist, maybe I did not understand your point.
Andres Aguado
