SCMEH-MO calculations on lanthanide systems V.: A comparison of DFT and SCMEH-MO methods on Nd(CO)6

Computations of electronic structure and bonding in the atypical lanthanide, Nd(CO)(6), have been carried out via approximate SCMEH-MO and more sophisticated DFT methods. A comparison of these results shows SCMEH-MO data to be more consistent with chemical bonding of Nd and CO than are the DFT data. In fact, the DFT density matrix breaks symmetry during the execution of the routine. But it is not at all understood why the symmetry-breaking had occurred. Consequently, the DFT final MOs do not conform to those required by O-h geometry. Over all, the Nd-CO bonding is weak and is not likely to promote pairing of four 4f electrons in one doubly degenerate MO, as shown in the DFT results. (C) 1998 Elsevier Science B.V.