# Origin of ultrastability in vapor-deposited glasses

## TL;DR

This study uses molecular simulations to understand how vapor deposition creates ultrastable glasses, revealing that surface relaxation is key and providing a quantitative relation for deposition efficiency.

## Contribution

It introduces a scaling relation linking vapor deposition efficiency to surface relaxation, clarifying the mechanism behind ultrastability in vapor-deposited glasses.

## Key findings

- Surface relaxation is crucial for ultrastability.
- A scaling relation quantifies vapor deposition efficiency.
- Vapor deposition mimics bulk relaxation processes.

## Abstract

Glass films created by vapor-depositing molecules onto a substrate can exhibit properties similar to those of ordinary glasses aged for thousands of years. It is believed that enhanced surface mobility is the mechanism that allows vapor deposition to create such exceptional glasses, but it is unclear how this effect is related to the final state of the film. Here we use molecular dynamics simulations to model vapor deposition and an efficient Monte Carlo algorithm to determine the deposition rate needed to create ultra-stable glassy films. We obtain a scaling relation that quantitatively captures the efficiency gain of vapor deposition over bulk annealing, and demonstrates that surface relaxation plays the same role in the formation of vapor-deposited glasses as bulk relaxation does in ordinary glass formation.