Calculation of NMR chemical shifts for taxol and alpha-pinene within the generalized gradient approximation

摘要

Simulations of the nuclear magnetic shielding within the generalized gradient approximation (GGA) for alpha-pinene and taxol were carried out to assess the performance of the method for bigger molecules. The localized orbital/local origin gauge (LORG) formalism and the modified "0.05" Becke's three-parameter exchange functional and the gradient-corrected functional of Lee, Yang, and Paar (B3LYP) proposed recently by Wilson and others was used. A modest dependence of the results on the basis set size was observed. For the current implementation, the uncoupled calculations were up to 47 times faster than the usual coupled-perturbed (CP)-gaugeinvariant atomic orbital (GIAO) method and provided similar accuracy. Reproducing both the absolute as the relative chemical shifts the GGA/LORG procedure can thus be used as a faster alternative to the coupled techniques.