Closed-shell compounds calculations

The inner core electrons occupy closed shells. The only exchange part of the two-electron Breit interaction between the valence, outer core and inner core electrons, Bf and P/c, gives non-zero contribution. The contributions from Bfy and P/c, are quite essential for calculation at the level of chemical accuracy (about 1 kcal/mol or 350 cm for transition energies). This accuracy level is, in general, determined by the possibilities of modern correlation methods and computers already for compounds of light elements. Note, that the contribution from the exchange interaction is not smaller than that from the Coulomb part [29]. The inner core electrons can be considered as frozen in most physical-chemical processes of interest. Therefore, the effective operators for P/ and P/c acting on the valence and... 

In the following we review quantum chemical work about organic germanium, tin and lead compounds which has been published since 1990. The presentation of the results is organized as follows. First, we discuss in brief some relevant theoretical work about parent compounds of Ge to Pb. Then we summarize calculations of organometallic compounds. The latter section is divided into studies of neutral closed-shell molecules, charged species and radicals. E is used for any of the group-14 elements C to Pb. 

ZINDO57-58 is a semiempirical intermediate neglect of differential overlap/spectroscopy (INDO/S) based routine. It can be combined with an SOS method to calculate second-order nonlinear optical coefficients. ZINDO is parametrized to accommodate transition-metal calculations and is therefore suited for calculation on organometallic compounds. To achieve computational efficiency, some of the terms in Eq. (2) are replaced by empirical data or neglected. To see how the INDO/S does this, the closed-shell case will be examined.57 58 It is useful to introduce the following ... 

We have seen that in es.sentially all transition-metal compounds, a possible starting point for a calculation of the electronic structure is an ionic description. In the perovskites, however, it may be determined from Table 19-3 that perturbation theory runs into trouble. We may, for example, calculate the effective charge Z on oxygen, starting with a closed shell 0 . The perturbation of each oxygen pa... 

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