An economic storage and processing method for two‐electron integrals in LCAO ‐ MO calculations

An economic algorithm for storing and processing two‐electron integrals arising in LCAO‐MO calculations is presented. The integrals are sorted prior to the SCF iterative scheme, classified according to equivalences in the orbital indices and finally stored on separate files that contain only integrals of one type. The novel approach of physically separating the integrals according to category is shown to be more efficient than random storage. Actual computing times for the new technique are tabulated for a representative number of molecular systems and compared with times obtained using previously reported methods.