Coulombic interactions dielectric model approximations

In contrast, EET has been historically modelled in terms of two main schemes the Forster transfer [15], a resonant dipole-dipole interaction, and the Dexter transfer [16], based on wavefunction overlap. The effects of the environment where early recognized by Forster in its unified theory of EET, where the Coulomb interaction between donor and acceptor transition dipoles is screened by the presence of the environment (represented as a dielectric) through a screening factor l/n2, where n is the solvent refractive index. This description is clearly an approximation of the global effects induced by a polarizable environment on EET. In fact, the presence of a dielectric environment not only screens the Coulomb interactions as formulated by Forster but also affects all the electronic properties of the interacting donor and acceptor [17],... 

The values me and mh are the effective masses of the electron and hole respectively. The second term describes the Coulombic interaction of the electron and the hole, where e is the universal charge and e is the dielectric constant of the material in question. Good correlation between theory and experiment has been obtained within this model for larger nanoclusters [78]. In the case of smaller particles, especially those smaller than 2 nm, the lowest exdted states are located in a region of the energy band that is no longer parabolic and, as a result, the effective mass approximation breaks down. For these partides a more molecular approach re-... 

Any of the methods used in classical Monte Carlo and molecular dynamics simulations may be borrowed in the combined QM/MM approach. However, the use of a finite system in condensed phase simulations is always a severe approximation, even when appropriate periodic or stochastic boundary conditions are employed. A further complication is the use of potential function truncation schemes, particular in ionic aqueous solutions where the long-range Coulombic interactions are significant beyond the cutoff distance.Thus, it is alluring to embed a continuum reaction field model in the quantum mechanical calculations in addition to the explicit solute—solvent interaaions to include the dielectric effect beyond the cutoff distance. - uch an onion shell arrangement has been used in spherical systems, whereas Lee and Warshel introduced an innovative local reaction field method for evaluation of long-... 

An alternative to the simple screened Coulomb interaction in protein modeling is the distance-dependent dielectric function [51]. In this approximation the effective electrostatic interaction between two partial charges q at distance r is written as... 

The results were analysed using HNC calculations described in another chapter of this book. The ion-ion correlations in the electrolyte and the ionic profiles in the vicinity of the water-air interface were calculated within the HNC integral equation approximation at the Primitive Model level of description (ionic spheres immersed in a continuous dielectric solvent). The (solvent-averaged) ion-ion interaction potential y(r) is the sum of a hard-sphere contribution (radii ), a generic Coulombic Contribution ZiZje / 47T oer) (valency Z, dielectric constant e = 78) and a specific dispersion contribution. ... 

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