Huckel

DESCRIPTION

This method keyword requests an extended Huckel calculation [Hoffmann63, Hoffmann64, Hoffmann64a, Hoffmann64b, Hoffmann66]. ExtendedHuckel is a synonym for this keyword. No basis set keyword should be specified.

OPTIONS

Hoffmann
Requests an Extended Huckel calculation using the default parameter set from the Huckel group.

Muller
Requests an Extended Huckel calculation using parameters collected by Edgar Muller.

Guess
Requests an Extended Huckel calculation using the modified parameters used for Guess=Huckel [Pyykko81, Pyykko84, Fitzpatrick86].

AVAILABILITY

Energies, “analytic” gradients and numerical frequencies.

EXAMPLE

The energy appears in the output file as follows (followed by the x, y, and z components of the dipole moment):

 Huckel eigenvalues -- -1.245  -0.637  -0.558  -0.544  -0.043  0.352
 Energy=   -5.968836513622 NIter=   0.
 Dipole moment=       0.000000       0.000000       0.000000

The energy is as defined by this semi-empirical model. Note that energy differences computed from the values in semi-empirical calculations are in Hartrees and may be compared directly with energy differences computed from jobs using other methods.

RELATED KEYWORDS

Guess=Huckel


Last updated on: 10 May 2009