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Semiempirical vs. Ab Initio Calculations of Molecular Properties. Part 3. Electric Field Gradients at 14N Nuclei in some Small Molecules

Z. B. Maksić ; Theoretical Chemistry Group, The Ruđer Bošković Institute, 41001 Zagreb, Yugoslavia
M. Primorac ; Faculty of Forestry, The University of Zagreb, 41000 Zagreb, Šimunska 25, Yugoslavia
S. Supek ; Faculty of Natural Sciences and Mathematics, The University of Zagreb, Marulićev trg 19, 41000 Zagreb, Yugoslavia

Sažetak

Electric field gradients (EFG) at nitrogen nuclei in some small
and medium size molecules are calculated by the semiempirical
CNDO/2Dand SCC-MO methods. A salient feature of our procedure
is accurate evaluation of matrix elements of the EFG operator.
Hence, comparison of EFG values with the results of more
sophisticated ab initio procedures obtained by suitable basis sets
indicates flaws and shortcomings of the semiernpirical schemes.
It is concluded that EFGs provide a sensitive test of the anisotropy
of the charge distribution of atoms in molecular environments.
Therefore, they are invaluable for parametrization purposes leading to optimal screening constants of valence AOs to be used in semiempirical theories. As to the performance of the present
CNDO/2D and SCC-MO methods, they provide only qualitative information about EFGs, the Iatter scheme being better because the CNDOj2D method fails to reproduce nuclear quadrupole coupling constants of nitriles.

Ključne riječi

Hrčak ID:

175871

URI

https://hrcak.srce.hr/175871

Datum izdavanja:

28.4.1988.

Posjeta: 762 *