ADDENDUM TO A RECENT PAPER BY HALGREN, LIPSCOMB, AND THEIR CO-WORKERS CONCERNING THE RELATIVE ACCURACIES OF SEVERAL CURRENT MO METHODS

The results of MNDO semiempirical molecular orbital calculations are compared with a standard set of test data previously suggested for the evaluation of currently employed MO procedures by Halgren, Lipscomb, arid their co-workers. The MNDO calculations which, for a single SCF cycle, require approximately the same computation time as CNDO/2 (geometry optimizations require ~1.5 SCF per variable) are 16 times more accurate than the latter method and about 3 times more accurate than PRDDO, STO-3G, or minimum basis set ab initio methods for the calculation of relative energies (MNDO calculation including geometry optimization; others at experimental geometries). For ionization potentials and dipole moments all methods perform similarly with the exception of CNDO/2, which is ~two and ~four times less accurate in the two cases. © 1979, American Chemical Society. All rights reserved.