Geometry Optimization Within a Modified Extended Hückel Formalism: Modifications to the ASED Program

Abstract The ASED program by Anderson and coworkers was modified to include a full geometry optimizer. It was discovered that, even with this modification, the ASED program could not be used to perform geometry optimizations on organic molecules without further modification. These modifications included changing the Wolfsberg-Helmholz equation used in the ASED program back to the original equation found in the FORTICON8 program as well as changing the Slater orbital exponents. A general parameter set for C, H, O and N has been developed, which has been used to perform geometry optimizations on selected organic molecules. The calculated geometries compared reasonably with the experimental values and with previously published AM1 geometries.

[1]  G. E. Leroi,et al.  Direct Observation of the Infrared Torsional Spectrum of C2H6, CH3CD3, and C2D6 , 1968 .

[2]  A. Anderson,et al.  Toward a better understanding of the atom superposition and electron delocalization molecular orbital theory and a systematic test: diatomic oxides of the first transition-metal series, bonding and trends , 1987 .

[3]  A. Anderson.  Derivation of the extended Hückel method with corrections: One electron molecular orbital theory for energy level and structure determinations , 1975 .

[4]  Roald Hoffmann,et al.  Conservation of orbital symmetry , 1968 .

[5]  G. Calzaferri,et al.  Molecular geometries by the Extended Hueckel Molecular Orbital (EHMO) method , 1989 .

[6]  W. Lipscomb,et al.  Theory of Polyhedral Molecules. I. Physical Factorizations of the Secular Equation , 1962 .

[7]  R. Hoffmann.  An Extended Hückel Theory. I. Hydrocarbons , 1963 .

[8]  R. Hoffmann,et al.  Counterintuitive Orbital Mixing in Semiempirical and ab Initio Molecular Orbital Calculations , 1978 .

[9]  M. Dewar,et al.  Ground States of Molecules. 38. The MNDO Method. Approximations and Parameters , 1977 .

[10]  B. Rabinovitch,et al.  Nitric Oxide Catalyzed Cis‐Trans Isomerization of Dideuteroethylene , 1955 .

[11]  Roald Hoffmann,et al.  Description of diatomic molecules using one electron configuration energies with two‐body interactions , 1974 .

[12]  Eamonn F. Healy,et al.  Development and use of quantum mechanical molecular models. 76. AM1: a new general purpose quantum mechanical molecular model , 1985 .