Electrostatic interactions, theoretical aspects

Several issues remain to be addressed. The effect of the mutual penetration of the electron distributions should be analyzed, while the use of theoretical densities on isolated molecules does not take into account the induced polarization of the molecular charge distribution in a crystal. In the calculations by Coombes et al. (1996), the effect of electron correlation on the isolated molecule density is approximately accounted for by a scaling of the electrostatic contributions by a factor of 0.9. Some of these effects are in opposite directions and may roughly cancel. As pointed out by Price and coworkers, lattice energy calculations based on the average static structure ignore the dynamical aspects of the molecular crystal. However, the necessity to include electrostatic interactions in lattice energy calculations of molecular crystals is evident and has been established unequivocally. 

Electrolyte solutions are non-ideal, with non-ideality increasing with increase in concentration. When experimental results on aspects of electrolyte solution behaviour are analysed, this non-ideality has to be taken into consideration. The standard way of doing so is to extrapolate the data to zero ionic strength. However, it is also necessary to obtain a theoretical description of non-ideality, and to deduce theoretical expressions which describe non-ideality for electrolyte solutions. Non-ideality is taken to be a manifestation of the electrostatic interactions which occur as a result of the charges on the ions of an electrolyte, and these interactions depend on the concentration of the electrolyte solution. Theoretically this non-ideaUty is taken care of by an activity coefficient for each ion of the electrolyte. 

The simplest sulfuranyl radicals of the cr type contain a halogen atom or small radical, like HS or HO, bonded to a dialkyl sulfide. Detailed structures of these do not appear to be available from experiment, but they have been investigated by theoretical methods. Figure 4 shows the structures of H2S C1 and H2SASH calculated at the MP2/4-3IG level by Clark [73]. An interesting aspect of the H2SASH geometry is the tendency of the H atom of SH to bend towards the S atom of the H2S. This was attributed to an electrostatic interaction. In both species the spin was found to remain primarily (ca. 98%) on the heavy atom of... 

In this paper we shall develop a new version of Coherent Potential Approximation theory (CPA). We apply a local external field and study the response of the mean field CPA alloy. Because of the fluctuation-dissipation theorem, the response to the external field must be equal to the internal field caused by electrostatic interactions. This new theoretical scheme, avoiding the consideration of specific supercells, will enable us to explore a broad range of fields and clarify certain aspects of the mentioned qV relations. 

In what follows, we first discuss the basic aspects of DFT in Section 6.2 and the electrostatic interaction model for polarizability in Section 6.3. The density-based theoretical formalism for electric response of clusters and suitable coarse graining forms the subject matter of Section 6.4. Miscellaneous aspects of polarizability calculation of metal clusters are discussed in Section 6.5 which is followed by presentation of concluding remaiks in Section 6.6. 

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