Atom Every atom is composed of a nucleus and one or more electrons bound to the nucleus. The nucleus is made of one or more protons and typically a similar number of neutrons. Protons and neutrons are called nucleons. More than 99.94% of an atom's mass is in the nucleus. The protons have a positive electric charge, the electrons have a negative electric charge, and the neutrons have no electric charge. If the number of protons and electrons are equal, that atom is electrically neutral. If an atom has more or fewer electrons than protons, then it has an overall negative
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