New parametrization scheme for the resonance integrals (H-mu nu) within the INDO/1 approximation. Main group elements

Among the currently available semiempirical methods, there is still no mode l equally good for both geometries and spectroscopy. We describe our recent attempt to obtain a set of parameters using the semiempirical INDO/1 model Hamiltonian. We have modified the formula for resonance integrals accordin g to a previous suggestion by Kolb and Thiel for MNDO, and developed a set of parameters for several elements belonging to the first and second rows o f the periodic table. This suggested set has been implemented in the latest versions of the ZINDO code and already represents a considerable improveme nt (relative to Pople's original INDO/1 parametrization) in the calculated geometries. Furthermore, this improved method is shown to be at least compe titive with the currently popular NDDO methods. In addition, the results of ionization potentials (calculated at the Koopmans' approximation) and tran sition energies show that the performance of the INDO/S technique in spectr oscopy has been preserved. (C) 2001 John Wiley gr Sons, Inc.