EFFICIENT IMPLEMENTATION OF THE GAUGE-INDEPENDENT ATOMIC ORBITAL METHOD FOR NMR CHEMICAL-SHIFT CALCULATIONS

An implementation of the gauge independent atomic orbital (GIAO) method for the ab initio self-consistent-field (SCF) calculation of nuclear magnetic resonance (NMR) chemical shifts is described. Using modern techniques borrowed from analytical derivative methods, we were able to improve the efficiency of the GIAO method significantly. Results with several basis sets, some of them large, are presented for methane, methyl fluoride, cyclopropene, cyclopropane, oxirane, benzene, carbon disulfide, the sulfate and thiosulfate anions, dimethyl sulfide, dimethyl sulfoxide, and dimethyl sulfone. Computer timings for energy and chemical shielding calculations are given for a few large organic molecules. Comparisons are made with the individual gauge for localized orbitals (IGLO) method of Schindler and Kutzelnigg, and with the localized orbital/local origin (LORG) method of Hansen and Bouman. The GIAO method appears to converge faster than the localized techniques; i.e., it provides the same accuracy with a smaller basis, particularly for the individual tensor components. The computational effort for the ab initio calculation of the NMR chemical shifts is only ~2.5 times of the energy calculation. © 1990, American Chemical Society. All rights reserved.