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

TL;DR

This paper presents a simple theoretical approach to estimate the bulk modulus of mixed ammonium halide crystals NH4Cl_{1-x}Br_x, aligning well with more complex models and providing insights into their elastic properties.

Contribution

It introduces a straightforward theoretical model to calculate the bulk modulus of mixed ionic crystals, complementing existing three-body potential models and Vegard's law.

Findings

Calculated bulk modulus values agree with TDPM results

Model effectively estimates elastic properties of mixed crystals

Provides a simpler alternative to complex computational methods

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.