ISSN:
0192-8651

Keywords:
parallel computation
;
SCF NMR chemical shifts
;
GIAO
;
pseudodiagonalization
;
Chemistry
;
Theoretical, Physical and Computational Chemistry

Source:
Wiley InterScience Backfile Collection 1832-2000

Topics:
Chemistry and Pharmacology
,
Computer Science

Notes:
We implemented our gauge-including atomic orbital (GIAO) NMR chemical shielding program on a workstation cluster, using the parallel 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. 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 The SCF diagonalization step, which is difficult to parallelize, has been replaced by pseudodiagonalization.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. © 1997 by John Wiley & Sons, Inc. J Comput Chem 18: 816-825, 1997

Additional Material:
1 Ill.

Type of Medium:
Electronic Resource

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