Jason Martin - Comments on the molecular geometry of ferrocene: The dangers of using quantum chemistry programs as black boxes

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      Publication Details (including relevant citation   information):

      Martin J., Baker J., and   Pulay P. J. Comp. Chem., 2008, 881

      Abstract:

      The dangers of using standard quantum chemistry programs as black   boxes is illustrated by analyzing some results in a recent paper   published in this journal (Zhang et al., J Comput Chem 2007, 28,   2260). The main danger is that nonlinear optimizations of both   the wavefunction and the molecular geometry may converge to   higher local minima or to saddle points, producing misleading   results. For instance, some of the calculated molecular   geometries of ferrocene in the aforementioned paper correspond to   an SCF solution that converged to an excited state. This is the   cause of the apparent large variation in the calculated iron-ring   distance with the basis set. Another problem we noticed is that   the source of the diffuse functions used in the earlier work in   connection with the 6-31G and 6-311G basis sets for transition   metals is not specified in the literature or the program manual.   They are also a poor match for the 6-31G basis set. We   re-emphasize that the 6-31G basis set used in this paper lacks   the necessary diffuse d-type functions for the late first-row   transition metals, and ought to be replaced by the m6-31G basis   that offers a more balanced description of the atomic valence   states. © 2008 Wiley Periodicals, Inc. J Comput Chem, 2009

      Address (URL): http://www3.interscience.wiley.com/journal/121401951/abstract?CRETRY=1&SRETRY=0