 Alternatively, the potential energy can be written in the embedded atom model form

formula_12

where formula_13 is the electron density at the location of atom formula_3.These two forms for the energy can be shown to be equivalent (in the special case that the bond-order function formula_4 contains no angular dependence).A more detailed summary of how the bond order concept can be motivated by the second-moment approximation of tight binding and both of these functional forms derived from it can be found in.