Сначала я думал, что происходит прямое решение РМХ в нужном базисе. И никак не мог понять как сопоставить потенциалы ионизации с конкретными базисными функциями. Потом в Вики прочитал, что всё происходит по другому Extended Hückel method
Стал искать подробную инфу об этом. Смотрел ссылки ГАМЕССа, там ничего нет. У ГАУССИАНа нашел только это:It is common in many theoretical studies to use the extended Hückel molecular orbitals as a preliminary step to determining the molecular orbitals by a more sophisticated method such as the CNDO/2 method and ab initio quantum chemistry methods. Since the extended Hückel basis set is fixed, the monoparticle calculated wavefunctions must be projected to the basis set where the accurate calculation is to be done. One usually does this by adjusting the orbitals in the new basis to the old ones by least squares method. As only valence electron wavefunctions are found by this method, one must fill the core electron functions by orthonormalizing the rest of the basis set with the calculated orbitals and then selecting the ones with less energy. This leads to the determination of more accurate structures and electronic properties, or in the case of ab initio methods, to somewhat faster convergence.
Вряд ли там есть нужная инфа. В общем хелп!R. Hoffmann, “An Extended Huckel Theory. I. Hydrocarbons,” J. Chem. Phys., 39 (1963) 1397.
R. Hoffmann, “An Extended Huckel Theory. II. Sigma Orbitals in the Azines,” J. Chem. Phys., 40 (1964) 2745.
R. Hoffmann, “An Extended Huckel Theory. III. Compounds of Boron and Nitrogen,” J. Chem. Phys., 40 (1964) 2474.
R. Hoffmann, “An Extended Huckel Theory. IV. Carbonium Ions,” J. Chem. Phys., 40 (1964) 2480.
R. Hoffmann, “Extended Huckel Theory. V. Cumulenes, Polyenes, Polyacetylenes and Cn,” Tetrahedron, 22 (1966) 521.