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466. DNMR4: Calculation of Chemically Exchanging
Spectra
by C. Hackett Bushweller, Leo J. Letendre, Jacques A. Brunelle, Howard S. Bilofsky, Michael R. Whalon and Stephen H. Fleischman, Department of Chemistry, University of Vermont, Burlington, Vermont 05405 DNMR4, a program for the calculation of chemical exchange NMR spectra, is a modification of DNMR3 (D. A. Kleier and G. Binsch, QCPE 165). The modifications are all intended to decrease CPU time and memory usage and improve numerical stability. These modifications involved replacing the eigenproblem subroutine ALLMAT with the EISPAK routines CBAL, COMHES, COMLR2 and CBABK2. In addition, the similarity transformation "trick" described by Gerhard Binsch in J. Mag. Resonance, 30, 625 (1978) was implemented to avoid explicit inversion of the eigenvector matrix. This required inclusion of the subroutine DEGEN to search for degenerate eigenvalues and the Schmidt orthogonalization of the corresponding eigenvectors. The complex matrices have been separated into two real matrices, and much of the arithmetic is thus real instead of complex. Memory usage was decreased approximately 30%, and CPU time usage was decreased up to 60%. We removed the coding that automatically averaged the spectra if the rate constant was 1000 times the largest chemical shift difference. Furthermore, the intensities are normalized to allow the separate calculation of noncoupled subspectra and the subsequent plotting of the additive spectra. FORTRAN (ANSI) Lines of Code: 2490 |