where F is the Fock matrix, C contains the molecular orbital coefficients and E is the diagonal matrix of the orbital energy eigenvalues. Given F, the corresponding C and E can then be determined either self-consistently (following Pople ) or via configuration interaction (following Pariser and Parr ), most often starting from a guess C from the corresponding Hückel model. The main computational effort is then to construct F, which has the following matrix elements 29