Eine Berechnung der Feldgradienten am Ort der Fe- und Co-Kerne in Fe (C5H5)2 und [Co (C5H5)2]+
The second part of this series on the field gradient in Fe(C5H5)2 and [Co(C5H5)2] + attains an improved choice of the radial parts of the atomic orbitals (AO’s) according to population analysis. Thus new overlap integrals are found which favour the use of BALLHAUSEN and DAHL coefficients for the LCAO expansion of the molecular orbitals (MO’s) of the molecules cited above. All contributions to the field gradients at the sites of the metal atom nuclei can be written down formally using these coefficients and the AO basis set. One-center integrals lead back to the 〈r-3〉nl-values obtained in part I of this series. COULSON’S Molecular Zeta Function is used in order to compute the occuring two-center integrals. The results are confirmed by the application of approximation formulas, especially one which takes account of the symmetry of the field gradient operator. Without inclusion of STERNHEIMER corrections the theoretical field gradients thus obtained are 2.367 a. u. in [Co (C5H5) 2] + and 1.58 a. u. in Fe(C5H5)2 compared with experimental values of 2.11 and 1.25 a. u. respectively.