EAST GEOMETRY OPTIMIZATION USING A MODIFIED EXTENDED HUCKEL-METHOD - RESULTS FOR MOLECULES CONTAINING H, C, N, O, AND F

A semiempirically parameterized version of the extended Huckel molecular orbital method has been combined with an efficient quasi-Newton Broyden-Fletcher-Goldfarb-Shannon (BFGS) optimization algorithm to obtain accurate geometries for compounds containing H, C, N, 0, and E The requirement of only one matrix diagonalization per energy evaluation makes the EHNDO (Extended Huckel Neglect of Differential Overlap) method faster than semiempirical Hartree-Fock NDDO methods such as MNDO, AM1, and PM3. Geometrical results for EHNDO appear to be as good as or better than results for the widely used AM1 technique, and geometry optimization for EHNDO also requires only a fraction of the time. (c) 1994 by John Wiley and Sons, Inc.