The CNDO equations

The form of the CNDO/2 equations for the Fock matrix comes from the basic approximation =5 y(]) j (]) j. This reduces the 

The elements of the CNDO/2 Fock matrix (for the RHF case) thus become 

In a ZDO computation where the overlap matrix is assumed to be the unit matrix, the diagonal elements of the density matrix 

It remains to specify the elements of the one-electron core Hamiltonian, Hj y, containing the kinetic energy and nuclear attraction integrals. 

The diagonal elements of the core Hamiltonian simply represent the energy of an electron in an atomic orbital of the corresponding atom, plus the attraction of an electron in that atomic orbital 

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The molecular orbital model vdiich has been developed to describe PES and UVA from aromatic hydrocarbons and heterocycles is a spectroscopically parameterized CNDO model, called the CND0/S3 model, constructed to describe these spectra for benzene (12), p-xylene (12), pyrolle (13), furan (14) and p-difluoroben-zene (15). The CNDO equations for the one electron orbitals are specified by Eqs. (lb)-(4b) in Lipari and Duke (1 ). The parameters utilized in these equations to define the CND0/S3 model are given in Table I. 

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