Calculation of the bulk modulus of mixed ionic crystal NH_4Cl_{1-x}Br_x

Abstract

The ammonium halides present an interesting system for study in view of their polymorphism and the possible internal rotation of the ammonium ion. The static properties of the mixed ionic crystal NH$_4$Cl$_{1-x}$Br$_x$ have been recently investigated, using three-body potential model (TDPM) by the application of Vegard's law. Here, by using a simple theoretical model, we estimate the bulk modulus of their ternary alloys NH$_4$Cl$_{1-x}$Br$_x$, in terms of the bulk modulus of the end members alone. The calculated values are comparable to those deduced from the three-body potential model (TDPM) by the application of Vegard's law.