Methods for parallel computation of SCF NMR chemical shifts by GIAO method: Efficient integral calculation, multi-Fock algorithm, and pseudodiagonalization
✍ Scribed by Wolinski, Krzysztof; Haacke, Robert; Hinton, James F.; Pulay, Peter
- Publisher
- John Wiley and Sons
- Year
- 1997
- Tongue
- English
- Weight
- 165 KB
- Volume
- 18
- Category
- Article
- ISSN
- 0192-8651
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✦ Synopsis
We implemented our gauge-including atomic orbital GIAO NMR chemical shielding program on a workstation cluster, using the parallel Ž . virtual machine PVM message-passing system. On a modest number of nodes, we achieved close to linear speedup. This program is characterized by several novel features. It uses the new integral program of Wolinski that calculates integrals in vectorized batches, increases efficiency, and simplifies parallelization.
Ž . The self-consistent field SCF step includes a multi-Fock algorithm, i.e., the simultaneous calculation of several Fock matrices with the same integral set, increasing the efficiency of the direct SCF procedure. The SCF diagonalization step, which is difficult to parallelize, has been replaced by pseudodiagonalization. The latter, widely used in semiempirical programs, becomes important in ab initio type calculations above a certain size, because the ultimate scaling of the diagonalization step is steeper than that of integral computation. Examples of the calculation of the NMR shieldings in large systems at the SCF level are shown. Parallelization of the density functional code is underway.