Local Properties of the Potential Energy Landscape of a Model Glass: Understanding the Low Temperature Anomalies

TL;DR

This study uses computer simulations to systematically identify double-well potentials in a model glass, revealing their localized or collective nature and their connection to the dynamics of different particle types, to better understand low temperature anomalies.

Contribution

Introduces a new algorithm for locating double-well potentials in a model glass, providing detailed insights into their properties and microscopic origins.

Findings

Most DWP are connected to smaller particle dynamics.

DWP related to larger particles are more collective.

Simulations are effective despite finite size and time limitations.

Abstract

Though the existence of two-level systems (TLS) is widely accepted to explain low temperature anomalies in the sound absorption, heat capacity, thermal conductivity and other quantities, an exact description of their microscopic nature is still lacking. We performed computer simulations for a binary Lennard-Jones system, using a newly developed algorithm to locate double-well potentials (DWP) and thus two-level systems on a systematic basis. We show that the intrinsic limitations of computer simulations like finite time and finite size problems do not hamper this analysis. We discuss how the DWP are embedded in the total potential energy landscape. It turns out that most DWP are connected to the dynamics of the smaller particles and that these DWP are rather localized. However, DWP related to the larger particles are more collective.