# A program system for ab initio MO calculations on vector and parallel processing machines III. Integral reordering and four-index transformation

## Description

Abstract This series of three papers presents a program system for ab initio molecular orbital calculations on vector and parallel computers. Part III is devoted to the four-index transformation on a molecular orbital basis of size NMO of the file of two-electron integrals (pq∥rs) generated by a contracted Gaussian set of size NATO (number of atomic orbitals). A fast Yoshimine algorithm first sorts the (pq∥rs) integrals with respect to index pq only. This file of half-sorted integrals labelled by thei... Title of program: ASTERIX-REORD, ASTERIX-TRANSF Catalogue Id: ABTA_v1_0 Nature of problem The evaluation of the correlation energy through Complete Active Space SCF iterations or CI expansion requires a file of two-electron integrals expressed over the basis of molecular orbitals (MOs) involved in the post-SCF treatment. Assuming that these MOs are known linear combinations of the initial atomic basis set, the present programs compute the integrals over the MO basis starting from a file of randomly distributed two-electron integrals expressed over the atomic orbital basis. Versions of this program held in the CPC repository in Mendeley Data ABTA_v1_0; ASTERIX-REORD, ASTERIX-TRANSF; 10.1016/0010-4655(91)90125-5 This program has been imported from the CPC Program Library held at Queen's University Belfast (1969-2018)