Thermoelastic Behaviour of Orientationally Disordered (NH4Br) x (KBr) 1-x

Abstract

We have incorporated the translational rotational (TR) coupling effects in the framework of three body force shell model (TSM) to develop an extended TSM (ETSM). This ETSM has been applied to reveal the second order elastic constants (C₁₁,C₁₂ and C₄₄) in the dilute regimes 0? x ? 0.50 as a function of temperature for 0K?T?320K. The anomalous elastic behaviour in C₄₄ has been depicted well by ETSM results in the orientationally disordered (NH₄Br) _x(KBr)_1-x mixed crystals. In order to present a visual comparison of the TR-coupling effect on second order elastic constants, we have evaluated the SOECs with and without TR coupling term in ETSM.

Keywords: Orientational glass, TR-coupling, Elastic constants.