A geometrical model for Mixed cyanide crystals

TL;DR

This paper presents a geometrical model that explains the physical features of mixed cyanide crystals, accurately predicting critical thresholds and transition behaviors in various alkali metal halogen compounds.

Contribution

The paper introduces a novel geometrical model based on diluted random fields to describe phase transitions in mixed cyanide crystals, aligning well with experimental observations.

Findings

Critical thresholds for phase transition disappearance are calculated exactly.

The model predicts first order transitions that become continuous with bromine dilution.

Results agree closely with experimental data on mixed cyanide crystals.

Abstract

A model of diluted random field sustained by quenched volume deformations is shown to reproduce puzzling physical features found in X(CN)_{x}Y_{1-x} mixed cyanide crystals. X is an alkali metal (K, Na or Rb) and Y is a spherical halogen ion (Br, Cl or I). Critical thresholds x_c at which associated first order ferroelastic transitions disappear are calculated exactly. The diluted random field is shown to compete with compressibility in making the transition first order. Transitions are then found to remain first order down to x_c except in the case of bromine dilution where they become continuous. All the results are in excellent agreement with available experimental data.