Extended Hückel method

The Extended Hückel Method (German: "Extended Hückel Method") is a semiempirical quantum chemical method that Roald Hoffmann developed in 1963.

The extended Hückel method is based on the Hückel method , but while the original Hückel method only considers the π orbitals, the extended method also includes the σ orbitals.

The Extended Hückel method can be used to determine the molecular orbitals or the relative energies of various geometric configurations, but it is not very successful in determining the structure optimization of an organic molecule. The electron correlation has only been looked at in a fairly simple way (the electron-electron repulsions are not explicitly included and the total energy is just a sum of terms for each electron in the molecule).

Individual evidence

^ R. Hoffmann: An Extended Hückel Theory. I. Hydrocarbons . In: J. Chem. Phys. . 39, No. 6, 1963, pp. 1397-1412. bibcode : 1963JChPh..39.1397H . doi : 10.1063 / 1.1734456 .
↑ M. Wolfsberg, LJ Helmholz: The Spectra and Electronic Structure of the Tetrahedral Ions MnO4−, CrO4−−, and ClO4− . In: J. Chem. Phys. . 20, No. 5, 1952, p. 837. doi : 10.1063 / 1.1700580 .

[1] R. Hoffmann: An Extended Hückel Theory. I. Hydrocarbons . In: J. Chem. Phys. . 39, No. 6, 1963, pp. 1397-1412. bibcode : 1963JChPh..39.1397H . doi : 10.1063 / 1.1734456 .

[2] M. Wolfsberg, LJ Helmholz: The Spectra and Electronic Structure of the Tetrahedral Ions MnO4−, CrO4−−, and ClO4− . In: J. Chem. Phys. . 20, No. 5, 1952, p. 837. doi : 10.1063 / 1.1700580 .