Calculation of nuclear magnetic shielding constants using variation-perturbation method with moderate size basis sets

Within a framework of variation-perturbation formalism of Karplus-Kolker, a n algorithm and a program for the nuclear magnetic shielding calculations w ith ground-state wave functions were developed. The calculations of nuclear magnetic shielding a in some diatomic molecules and also in methane, water and CH3F molecules with 6-311G ab initio wave functions were carried out. The results were compared with the experimental data and the results obtain ed by other theoretical methods. This method can be considered as an altern ative approach for the calculations of the magnetic anisotropic effects on chemical shifts and can be used for predicting the tendencies in magnetic s hielding alteration due to the different fragments in a big molecular syste ms. (C) 2001 Elsevier Science B.V. All rights reserved.