The potential energy component corresponding to the electrostatic interaction between each pair of charged particles: where is the permittivity of a vacuum, is the distance between the two particles, and and are the charges on particles and . In molecular orbital theory, the electrostatic repulsion between the two electrons occupying the orbitals and . In the Hartree –Fock method, the mean Coulomb repulsion is determined by the value of the Coulomb integral See also: exchange repulsion