Alkali halides shell model

Shell models have been used successfully in a wide variety of systems. The greatest number of applications have been in the simulation of ionic materials,especially systems including alkali halides, oxides,and zeolites. " The shell model is also commonly used for the simulation of molten and shell-type models... 

Scattering by Alkali Halides Melts A Comparison of Shell-Model and Rigid-Ion Computer Simulation Results. 

CsF is the only alkali halide with rocksalt structure in which the cation makes the greater contribution to the electronic polarizability. Although there have not been any Shell Model calculations on this material, its mirror compound Nal should provide at least some guide as to the energetics of... 

The effects of relaxation on the calculated surface phonon dispersion in Rbl have apparently been verified, particularly by the observation of a surface optical mode which lies above the bulk phonon optical bands. Except for the mysterious acoustic band mode in Rbl, the Shell model calculations have generally been quite accurate in predicting surface vibrational mode energies in both high-symmetry directions of the alkali halide (001) surfaces. 

Valence density depends on the periodic position of an atom, shown for representative elements in Table 14. The simplest situation to model is the polarization that occurs in an alkali halide molecule, also responsible for the largest dipole moments of diatomic molecules. In effect, a singly charged valence shell interacts with a single vacancy in the valence shell of the halogen atom. The polarization of the alkali shell should decrease with atomic size, which is measured by the period number of the valence shell. The implied decrease in valence density from Li to Na, of 8.6/6.4 3/2, suggests v = 1/n as approximate scale factor, which could be complicated by the appearance of (3 and / sublevels.lt is a complementary vacancy density that should be taken into account. 

The frequency dependence of the damping and shift of the TO-mode at q = 0 has also been calculated for NaCl [5.50]. A breathing shell model was used to provide frequencies and eigenvectors necessary for these calculations. The influence of anharmonicity on the TO and LO optical phonons at q = 0 has been studied experimentally by means of the far-infrared dielectric response for 18 alkali and thallium halides [5.51], for the silver and thallium halides... 

In describing the properties of complex species in alkali metal halide melts and the electrochemical processes involving these species, the anionic complex should be considered integral with its outer-sphere (OS) cationic shell [1-4], In model calculations, the composition of this shell is chosen rather arbitrarily. However, calculations show that, in many cases, variations in the composition of the second coordination sphere in the model system radically changes the resulting correlations. Therefore, the task is to search for criteria that permit determining the composition of the dominant complex species in alkali metal halide. 

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