English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Global: Zendy Plus annual

Presents the access of premium content as premium feature

Premium Content

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Global: Zendy Plus monthly

Global: Zendy Tools annual

Global: Zendy Tools monthly

Global: Zendy Free Plan

The mechanism of the vacancy ordering in metastable cubic Ge-Sb-Te (c-GST)that underlies the ultrafast phase-change dynamics and prominent thermoelectricproperties remains elusive. Achieving a comprehensive understanding of thevacancy-ordering process at an atomic level is challenging because of enormouscomputational demands required to simulate disordered structures on largetemporal and spatial scales. In this study, we investigate the vacancy orderingin c-GST by performing large-scale molecular dynamics simulations using machinelearning potentials. The initial c-GST structure with randomly distributedvacancies rearranges to develop a semi-ordered cubic structure with layer-likeordered vacancies after annealing at 700~K for 100~ns. The vacancy orderingsignificantly affects the lattice dynamical properties of c-GST. In the initialstructure with fully disordered vacancies, we observe a boson peak, usuallyassociated with amorphous solids, that consists of localized modes at$\sim$0.575~THz. The boson peak modes are highly localized around specificatomic arrangements of straight vacancy-Te-vacancy trios. As vacancies becomeordered, the boson peak disappears and the Debye-Waller thermal \textit{B}factor of Te decreases substantially. This finding indicates that the c-GSTundergoes a transition from amorphous-like to crystalline-like solid state bythermal annealing in low-frequency dynamics.

Study of vacancy ordering and the boson peak in metastable cubic Ge-Sb-Te using machine learning potentials