Analysis of the dielectric properties of mixed alkali halide crystals

Abstract

The electronic and static dielectric constants, longitudinal and transverse optic mode frequencies, effective charge parameters, optic mode Gruneisen parameters, and volume derivatives of dielectric constants are calculated for the entire range of composition of mixed NaC1-NaBr, KCI-KBrand KBr-KI crystals. The calculations are performed using the knowledge of interionic potentials. The results are discussed and compared with available experimental data.Die elektronische und die statische Dielektrizitatskonstante, die Frequenzen der longitudinalen und transversalen optischen Mode, die effektive Ladung, die Griineisenparameter der optischen Mode sowie die Volumenableitungen der Dielektrizitatskonstanten werden fur den gesamten Zusammensetzungsbereich der Mischkristalle NaC1-NaBr, KC1-KBr und KBr-KJ berechnet. Die Berechnungen werden mit den Kenntnissen iiber die Interionenpotentiale durchgefiihrt. Die Ergebnisse werden diskutiert und mit vorhandenen experimentellen Werten verglichen.

Theoretical analysis of static properties of mixed ionic crystal: NH4Cl1−x Br x

“…Here the first term is the Coulombic energy, second term is the TBI, third and fourth terms are the vdW energy due to dipole-dipole (d-d) and dipole-quadrupole (d-q) interactions, the fifth and sixth terms are the short-range repulsive energy terms due to the overlap repulsion between the nearest (ij) and the next-nearest neighbours (ii and jj) [22][23][24][25][26].…”

“…The solid rectangles and triangles indicate the experimental and other theoretical works[24][25][26].…”

“…The solid rectangles and triangles indicate the experimental and other theoretical works[24][25][26].effect of NH 4 Cl x Br 1−x which are given in table 4. Experimental values available for extreme ends have also been listed for comparison and we found that the values which we obtained are in closer agreement with the experimental results for the extreme ends.Table 4also gives the molecular force constant f and restrahlen frequencies ν 0 with and without Lorentz field effect for NH 4 Cl x Br 1−x mixed ionic solids.…”

Evaluation of Electronic Dielectric Constant and Fractional Ionic Character of Mixed Alkali Halide Crystals

“…I n a recent paper Shanker and Jain [9] investigated the dielectric properties of mixed NaC1-NaBr, KC1-KBr, and KBr-KI crystals. Some other mixed systems also known as solid solutions such as CsC1-CsBr, CsCI-RbCI, and CsCI-KC1 belonging to the same family of alkali halides have also been the subject of earlier investigations [lo, 111.…”

“…Recently there have been numerous attempts to investigate various properties of mixed alkali halide crystals [l to 81 which are of great scientific and technological importance. I n a recent paper Shanker and Jain [9] investigated the dielectric properties of mixed NaC1-NaBr, KC1-KBr, and KBr-KI crystals. Some other mixed systems also known as solid solutions such as CsC1-CsBr, CsCI-RbCI, and CsCI-KC1 belonging to the same family of alkali halides have also been the subject of earlier investigations [lo, 111. The different systems of mixed alkali halides can be classified in several manners, viz.…”