High pressure structural and lattice dynamics study of {\alpha}-In$_2$Se$_3$

TL;DR

This study investigates the high-pressure structural and lattice dynamics of layered $ ext{ extalpha}$-In$_2$Se$_3$ using synchrotron X-ray diffraction and Raman spectroscopy, revealing phase transitions and stability up to 45 GPa.

Contribution

It provides detailed experimental insights into the pressure-induced phase transitions and stability range of $ ext{ extalpha}$-In$_2$Se$_3$ using combined XRD and Raman techniques.

Findings

Pressure induces a phase transition from $ ext{ extalpha}$-In$_2$Se$_3$ to monoclinic $eta$'-In$_2$Se$_3$ at ~1 GPa.

The $eta$'-In$_2$Se$_3$ phase remains stable up to 45 GPa.

Beyond 45 GPa, In$_2$Se$_3$ adopts a disordered orthorhombic structure.

Abstract

Layered $\alpha$-In$_2$Se$_3$has been studied using a concomitant in-situ synchrotron angle dispersive powder x-ray diffraction and Raman spectroscopy study in a diamond anvil cell up to 60+ GPa, at room temperature. Helium, that remains fairly hydrostatic up to the highest pressure in this study, was used as the pressure-transmitting medium. The results from both experimental methods reveal a pressure-induced structural phase transition from $\alpha$-In$_2$Se$_3$ to a monoclinic $\beta$'-In2Se3 structure at $\approx$1 GPa, in agreement with previous studies. Based on our detailed measurements using both experimental techniques and F-f formalism, the $\beta$'-In$_2$Se$_3$ structure remains stable up to 45 GPa, without a clear indication of a phase transition towards the previously reported $\beta$-In2Se3 phase. Above this pressure, In$_2$Se$_3$ adopts a disordered solid-solution-like orthorhombic structure, phase IV. The results are discussed in comparison with the relevant previous studies of $\alpha$-In$_2$Se$_3$ under pressure.