To bring an ion of species "i", initially far away, to a point formula_58 within the ion cloud requires interaction energy in the amount of formula_92, where formula_10 is the elementary charge, and formula_94 is the value of the scalar electric potential field at formula_58. If electric forces were the only factor in play, the minimal-energy configuration of all the ions would be achieved in a close-packed lattice configuration. However, the ions are in thermal equilibrium with each other and are relatively free to move. Thus they obey Boltzmann statistics and form a Boltzmann distribution. All species' number densities formula_96 are altered from their bulk (overall average) values formula_97 by the corresponding Boltzmann factor formula_98, where formula_14 is the Boltzmann constant, and formula_15 is the temperature. Thus at every point in the cloud