Parallelization of four-component calculations. I. Integral generation, SCF, and four-index transformation in the Dirac-Fock package MOLFDIR

The treatment of relativity and electron correlation on an equal footing is essential for the computation of systems containing heavy elements. Correl ation treatments that are based on four-component Dirac-Hartree-Fock calcul ations presently provide the most accurate, albeit costly, way of taking re lativity into account. The requirement of having two expansion basis sets f or the molecular wave function puts a high demand on computer resources. Th e treatment of larger systems is thereby often prohibited by the very large run times and files that arise in a conventional Dirac-Hartree-Fock approa ch. A possible solution for this bottleneck is a parallel approach that not only reduces the turnaround time but also spreads out the large files over a number of local disks. Here, we present a distributed-memory paralleliza tion of the program package MOLFDIR for the integral generation, Dirac-Hart ree-Fock and four-index MS transformation steps. This implementation scales best for large AO spaces and moderately sized active spaces. (C) 2000 John Wiley & Sons, Inc.