Atom of Ernest Rutherford, bombarded a metal foil with alpha particles to observe how they scattered. They expected all the alpha particles to pass straight through with little deflection, because Thomson's model said that the charges in the atom are so diffuse that their electric fields could not affect the alpha particles much. However, Geiger and Marsden spotted alpha particles being deflected by angles greater than 90°, which was supposed to be impossible according to Thomson's model. To explain this, Rutherford proposed that the positive charge of the atom is concentrated in a tiny nucleus at the center of the atom.
Embedded atom model a simulation, the potential energy of an atom, formula_1, is given by where formula_3 is the distance between atoms formula_1 and formula_5, formula_6 is a pair-wise potential function, formula_7 is the contribution to the electron charge density from atom formula_5 of type formula_9 at the location of atom formula_1, and formula_11 is an embedding function that represents the energy required to place atom formula_1 of type formula_13 into the electron cloud. Since the electron cloud density is a summation over many atoms, usually limited by a cutoff radius, the EAM potential is a multibody potential. For a single element system