A molecular dynamics simulation of thermalization of crystalline lattice with harmonic interaction

TL;DR

This study uses molecular dynamics simulations of a harmonic lattice to explore the detailed microscopic processes and distinct relaxation behaviors during thermalization in crystalline solids.

Contribution

It reveals new insights into the relaxation rates, frequency proliferation, and out-of-plane deformation dynamics in a harmonic lattice model.

Findings

Transverse and longitudinal velocity components relax at different rates.

Power law governs nonlinear frequency proliferation.

Out-of-plane deformations show two-stage fluctuation behaviors.

Abstract

Understanding the realization of thermal equilibrium through the thermalization process in a many-body system is a fundamental and complex scientific question, bridging thermodynamics and classical dynamics and connecting to a host of physical phenomena, such as mechanical instabilities in a thermal environment. In this work, based on the harmonic lattice model, we investigate the thermalization process in both velocity and coordinate spaces, by examining microscopic dynamics on the atomic level. We show the distinct relaxation rates of the transverse and longitudinal components of the velocity, reveal the power law governing the nonlinear proliferation of dominant frequencies, and observe the concurrent rapid proliferations of frequencies and topological defects. We also show that the lattice system's persistent out-of-plane deformations exhibit two-stage fluctuation behaviors, characterized by distinct power laws of fractional exponents and associated with the broken up-down symmetry. This work demonstrates the rich dynamics underlying the thermalization process, and advances our understanding on the dynamical adaptations of many-body systems to external disturbances.