No worries .. I´m not offended. Discussion belong to science! ;) Well... let me put in this way: Classical Molecular dynamics is an approximation which works where the electronic degrees of freedom does play any role on your system. That is fine and I love it!
BUT , every time you are referring to chemical process - where electrons are fundamental - a there are other terminologies which are by far more accurate than the molecular dynamics one. In molecular dynamics all chemical bonds are represents - I mean represented - by springs ... so it is obvoious that what dou you have in the and is a potential energy! But that is not true if if you are comparing quantum levels ... it doesn't matter if HF, CI or KS ones - because in this energies what you have are components of the electronic kinetic energy plus all the potential terms. And by potentiual terms I mean the electrostatic interactions of the electrosn with their couter parts in the system plus the interactions with the external field! In this sense ... calling the E_KS energy as the "potential energy" is simply misleading! Cheers Ney On Fri, Feb 18, 2011 at 4:54 PM, aguado <[email protected]>wrote: > > > 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
