L. Oleari

The evaluation of the one-centre integrals in the semi-empirical molecular orbital theory

An expression is given which fairly accurately provides valence-state energies. It is shown that one can formally attribute the meaning of the one-centre integrals to the coefficients in such an expression. In this way one also obtains the criteria of Pariser and Parr. Moreover, if one introduces such semi-empirical integrals in the expression which gives the vertical ionization potentials and electron affinities, one obtains the corresponding experimental values. On the basis of these facts usage of such semi-empirical integrals in the M.O.-L.C.A.O. theory is proposed. A discussion of the advantages and the limitations of its application is made.

The spectra and electronic structure of tetrahedral ions

An S.C.F.-M.O.-L.C.A.O. calculation in the Roothaan-Popie scheme, using the Pariser-Parr approximations, has been carried out for the ions [CrO4]-- and [MnO4]-. The necessary integrals have been evaluated semi-empirically. For a more exact evaluation of the spectral transitions, a configuration interaction calculation, extended to the most important mono-excited configurations, has been performed. The order of levels previously suggested by Ballhausen and Liehr and other authors is confirmed by the results of the calculations. A new spectral assignment is presented, attributing to each observed absorption band two electronic transitions occurring between one of the occupied M.O.s (t 1, 2t 2, 1t 2) and the two lowest empty M.O.s (2e, 3t 2).

Molecular orbital theory for metal-halides complexes. the electronic structure and the spectrum of [PdCl4]2− ion

Abstract The electronic structure of the ground state is studied by semiempirical SCF-MO-LCAO calculations. An assignment of the electronic spectrum is given on the basis of both a configuration interaction calculation and some SCF calculations for lowest ecxited states.