# Vapor Condensed and Supercooled Glassy Nanoclusters

## TL;DR

This study uses molecular simulations to compare vapor condensed and supercooled glassy nanoclusters, revealing their structural stability, inhomogeneous dynamics, and similarities in low energy configurations despite different formation methods.

## Contribution

It demonstrates that vapor condensed and supercooled nanoclusters access similar low energy states and exhibit inhomogeneous relaxation dynamics, expanding understanding of nanocluster glass formation.

## Key findings

- Nanoclusters with similar energies are structurally alike regardless of formation history.
- Core regions become glassy above the glass transition, while surfaces remain mobile.
- Vapor condensed nanoclusters are more stable than ultra-stable glassy thin films.

## Abstract

We use molecular simulation to study the structural and dynamic properties of glassy nanoclusters formed both through the direct condensation of the vapor below the glass transition temperature, without the presence of a substrate, and \textit{via} the slow supercooling of unsupported liquid nanodroplets. An analysis of local structure using Voronoi polyhedra shows that the energetic stability of the clusters is characterized by a large, increasing fraction of bicapped square antiprism motifs. We also show that nanoclusters with similar inherent structure energies are structurally similar, independent of their history, which suggests the supercooled clusters access the same low energy regions of the potential energy landscape as the vapor condensed clusters despite their different methods of formation. By measuring the intermediate scattering function at different radii from the cluster center, we find that the relaxation dynamics of the clusters are inhomogeneous, with the core becoming glassy above the glass transition temperature while the surface remains mobile at low temperatures. This helps the clusters sample the highly stable, low energy structures on the potential energy surface. Our work suggests the nanocluster systems are structurally more stable than the ultra-stable glassy thin films, formed through vapor deposition onto a cold substrate, but the nanoclusters do not exhibit the superheating effects characteristic of the ultra-stable glass states.