Boson Peak decouples from elasticity in glasses with low connectivity

TL;DR

This study uses molecular dynamics simulations to explore how the boson peak in glasses is influenced by connectivity and elasticity, revealing that in low-connectivity systems, the boson peak is decoupled from elastic properties.

Contribution

It demonstrates that the boson peak in low-connectivity glasses is governed by non-bonding interactions and is decoupled from macroscopic elasticity, challenging previous interpretations.

Findings

Boson peak differs in crystals and glasses in elastic scaling.

Polymeric glass boson peak aligns with atomic glasses, driven by non-bonding interactions.

Elasticity does not fully explain the boson peak in low-connectivity systems.

Abstract

We perform molecular-dynamics simulations of the vibrational and the elasto-plastic properties of polymeric glasses and crystals and corresponding atomic systems. We evidence that the elastic scaling of the density of states in the low-frequency boson peak (BP) region is different in crystals and glasses. Also, we see that the BP of the polymeric glass is nearly coincident with the one of the atomic glasses, thus revealing that the former - differently from elasticity - is controlled by non-bonding interactions only. Our results suggest that the interpretation of the BP in terms of macroscopic elasticity, discussed in highly connected systems, does not hold for systems with low connectivity.