INDO/S-CI method

The ionization potentials, singlet and triplet excited states, and frontier molecular orbitals of 1,4-, 1,8-, and 4,5-diazafluorenones were investigated by the all-valence-electrons INDO/S-CI method. Calculated molecular properties were found to be in accordance with experimental results... 

Kotzian et al. (1991) and Kotzian and Rosch (1992) applied their INDO/1 and INDO/S-CI methods to hydrated cerium(III), i.e. model complexes [Ce(H20) ] (n=8,9), in order to rationalize the electronic structure and the electronic spectrum of these species. Besides the scalar relativistic effects spin-orbit coupling was also included in the INDO/S-CI studies. The spin-orbit splitting of the 4f F and 5d states of the free Ce " ion was calculated as 2175cm" and 2320cm in excellent agreement with the experimental values of 2253 cm and 2489 cm" , respectively. The calculated energy separation between the F and states of approximately 44000cm" (estimated fi-om fig. 5 in Kotzian and Rosch 1992) is somewhat lower than the experimental value of 49943 cm" (Martin et al. 1978). 

There are several theoretical studies on LaO and related lanthanide oxides. We have already mentioned the ligand-field theory model calculations of Field (1982) as well as Carette and Hocquet (1988). More recently, Kotzian et al. (1991a,b) have applied the INDO technique (Pople et al. (1967) extended to include spin-orbit coupling [see also Kotzian et al. (1989a, b)] to lanthanide oxides (LaO, CeO, GdO and LuO). The authors call it INDO/S-CI method. The INDO parameters were derived from atomic spectra, model Dirac Fock calculations on lanthanide atoms and ions to derive ionization potentials, Slater-Condon factors and basis sets. The spin-orbit parameter is derived from atomic spectra in this method. 

Table 52, reproduced from Kotzian et al. s work, compares the INDO/SCI energy separations with experiment for several electronic states of LaO. It is evident from table 52 that the INDO/S-CI method predicts the energy separations for these compounds reasonably well. Kotzian et al. also computed the transition moments for the observed A<->C, B<- X, C<- X, D<- X and F<- X systems. 

Kotzian et al. (1991a, b) as well as Kotzian and Rosch (1991a, b) have applied the INDO/S-CI method extended to include spin-orbit coupling on the diatomic CeO. They have studied 16 electronic states of CeO arising from the 4f6s configuration of Ce" at the experimental of 1.820A. The results of their computations are shown in... 

SCF/CISD methods in conjuction with quasi-relativistic ECPs. More recently, Kotzian et al. (1991a,b) have used the INDO/S-CI method to compute the energy separations of 45 12 electronic states of GdO. We use the Kotzian et al. (1991a, b) and the Dolg et al. (1990a,b) works as the basis for discussion on the electronic states of GdO. 

Kotzian et al. (1991b) have considered several structures of 03, D3, 3 and C3 symmetries. They noted that the agreement with the experimental spectrum could be obtained for a geometry with low symmetry, (i.e., with the three-fold axis removed) although for simplicity, Kotzian et al. (1991a, b) considered [Ce(H20)9] complex as if it had point-group symmetry. The INDO/S-CI method confirmed the previous... 

Intermediate neglect of differential overlap/spin-orbit Cl method (INDO/S-CI)... 

The spin-orbit Cl part of the INDO/S-CI is an adaptation of the Pitzer doublegroup Cl approach which we have already described. This method has been applied by Zerner, Rosch and co-workers for several lanthanide compounds such as LaO, CeO, GdO, LuO, PrO, etc. We will describe the results of these calculations is section 6. 

Fig, 43. Energy-level diagram for TmO as obtained from INDO/S-CI and LFT methods. All states are derived from the low-lying Tm H and F atomic terms. Formally assigned states ate indicated by empty boxes while the F derived states are indicated by hatched boxes. Reproduced from Kotzian and Rosch... 

Several attempts have been made to include Rydberg states within the INDO/S scheme, but they have not proven generally useful. See for example, D. R. Salahub and C. Sandorfy, Theor. Chim. Acta, 20, 111 (1971). CNDO, INDO, and RCNDO-CI Calculations on the Electronic Spectra of Saturated Hydrocarbons. W. Haque, /. Chon. Phys., 67, 3629 (1977). Use of the RINDO Method in Spectroscopy. Molecular Rydberg S -S and T<-T Transitions. 

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