Hi, given the scenario of an electron and a positron (both assumed to be stationary) being separated by a given distance how could i compute the energy of that system ? The total energy would certainly contain the rest-mass-energies of both particles, but i'm struggling to incorporate the electro-static energy (the usual electro static potential does not seem to be of help as it would suggest it requires infinite amounts of energy to separate the orignally superimposed electron/positron in the first place, or do i miss something here ?). So mathematically: E = 2mec2 + f(separation) But what would f(separation) look like ? Can somebody help me here ?