SEARCH Articles Figures Tables Approximations potentials Coupled Electron Pair Approximation Coupled approximation Coupled pair approximation Coupled-electron pair Coupling potential energy Electron coupled Electron coupling Electron pairing energy Electron-pairing approximation Electronic coupling Electronic energy potential Electronic potentials Energy approximation Pair approximation Pair coupling Pair energy Pair potential Pair potential approximation Pair potential energy Potential energy electron Surface electron potential Surface electronic Surface electrons