Pressure-induced phonon-freezing in the ZnBeSe alloy: a study via the percolation mesoscope

TL;DR

This study investigates how pressure affects phonon modes in ZnBeSe alloys, revealing a phonon-freezing phenomenon where stretching modes vanish and only bending modes remain near phase transition, combining experimental and computational insights.

Contribution

It introduces a mesoscopic percolation model combined with ab initio calculations to explain pressure-induced phonon behavior in ZnBeSe alloys, highlighting phonon-freezing phenomena.

Findings

Be-Se stretching mode freezes under pressure

Bending mode persists near phase transition

Supports mesoscopic and microscopic modeling approaches

Abstract

We use the 1-bond -> 2-phonon percolation doublet of zincblende alloys as a mesoscope for an unusual insight into their phonon behavior under pressure. We focus on (Zn,Be)Se and show by Raman scattering that the original Be-Se doublet at ambient pressure, of the stretching-bending type, turns into a pure-bending singlet at the approach of the high-pressure ZnSe-like rocksalt phase, an unnatural one for the Be-Se bonds. The freezing of the Be-Se stretching mode is discussed within the scope of the percolation model (mesoscopic scale), with ab initio calculations in support (microscopic scale).