Pressure-Induced Phase Transformation in $\beta$-Eucryptite: an X-Ray Diffraction and Density Functional Theory Study

TL;DR

This study combines in situ X-ray diffraction and density functional theory to investigate pressure-induced phase transformations in $eta$-eucryptite, revealing a new stable phase and two potential polymorphs under pressure.

Contribution

It identifies the atomic structure of the pressure-stabilized phase of $eta$-eucryptite and proposes two additional possible polymorphs, advancing understanding of its high-pressure behavior.

Findings

Pressure stabilizes a new phase with Pna2$_1$ symmetry.

Two additional pressure-stabilized polymorphs identified: P1c1 and Pca2$_1$.

Atomic structure of the new phase characterized through combined experimental and theoretical methods.

Abstract

Certain alumino-silicates display exotic properties enabled by their framework structure made of corner-sharing tetrahedral rigid units. Using \textit{in situ} diamond-anvil cell x-ray diffraction (XRD), we study the pressure-induced transformation of $\beta$ eucryptite, a prototypical alumino-silicate. $\beta$ eucryptite undergoes a phase transformation at moderate pressures, but the atomic structure of the new phase has not yet been reported. Based on density functional theory stability studies and Rietveld analysis of XRD patterns, we find that the pressure-stabilized phase belongs to the Pna2$_1$ space group. Furthermore, we discover two other possible pressure-stabilized polymorphs, P1c1 and Pca2$_1$.