C. Vanwullen et al., COMMENT ON THEORETICAL CALCULATIONS OF THE NUCLEAR MAGNETIC SHIELDINGTENSORS FOR THE ETHYLENIC CARBON-ATOMS IN CYCLOPROPENES, Molecular physics, 81(6), 1994, pp. 1373-1382
We compare several methods for the calculation of NMR shielding tensor
s at the Hartree Fock level (most of them using some sort of distribut
ed gauge origins), applied to the C-13 shielding tensors in cycloprope
ne C3H4 and its dichloro and tetrachloro derivatives, C3H2Cl2 and C3Cl
4. Among these methods is one recently proposed by Smith et al. that i
n our opinion should not be called IGLO. Since multiconfiguration IGLO
calculations indicate that correlation effects are important in these
molecules, the quality of Hartree-Fock based methods cannot be judged
from a comparison with experiment. Instead a comparison with the Hart
ree-Fock limit is necessary. Therefore IGLO benchmark calculations for
these molecules using large basis sets are presented.