PARALLEL DIRECT SCF FOR LARGE-SCALE CALCULATIONS

Quantum chemistry has become an essential tool in many areas of chemical research; however, quantum chemistry is not yet playing a role in many exciting new chemical disciplines, such as medicinal chemistry and materials science, where the size of the chemical systems has been too large to study using ab initio chemical methods. The development of massively parallel supercomputers offers the potential to predict properties relevant to a variety of problems in these burgeoning new fields. The goal of this project is to develop a set of parallelized ''production codes'' for initially a relatively limited set of methods. As a key part of this project we are experimenting with the use of modern programming languages and methodologies to make these programs both portable and reusable. This paper describes the development of a massively parallel direct SCF program, MPSCF. For systems over a few hundred basic functions, MPSCF running on 256 nCUBE processors performs nearly as well as Gaussian 90 running on a single processor Cray Y-MP. On the next generation of parallel computers, such as the Intel Touchstone Delta, MPSCF should allow the SCF calculations on chemical systems too large for vector supercomputers.