Theory of self-consistent electron pairs. An iterative method for correlated many-electron wavefunctions

A rapidly converging iterative method is presented to solve the many-electron Schrödinger equation within a Hilbert space confined to functions with at most two electrons outside an internal space defined by the orbitals of a reference function. The wavefunction is given in terms of external two-electron clusters represented by coefficients and density matrices referring directly to the basis functions. All matrix elements are obtained from generalized Coulomb and exchange operators. Only one operator per correlated electron pair is required for each iteration cycle.