Homogeneous nonequilibrium molecular dynamics method for heat transport and spectral decomposition with many-body potentials

TL;DR

This paper introduces a generalized homogeneous nonequilibrium MD method for realistic many-body potentials and spectral decomposition to efficiently compute and analyze thermal transport properties in complex materials.

Contribution

It extends the homogeneous nonequilibrium MD method to many-body potentials and develops a spectral decomposition approach that avoids lattice dynamics calculations.

Findings

The method is 10-100 times more efficient than Green-Kubo.

Accurately computes thermal conductivities of silicon, graphene, and carbon nanotubes.

Provides insights into thermal conductivity convergence in nanotubes.

Abstract

The standard equilibrium Green-Kubo and nonequilibrium molecular dynamics (MD) methods for computing thermal transport coefficients in solids typically require relatively long simulation times and large system sizes. To this end, we revisit here the homogeneous nonequilibrium MD method by Evans [Phys. Lett. A \textbf{91}, 457 (1982)] and generalize it to many-body potentials that are required for more realistic materials modeling. We also propose a method for obtaining spectral conductivity and phonon mean free path from the simulation data. This spectral decomposition method does not require lattice dynamics calculations and can find important applications in spatially complex structures. We benchmark the method by calculating thermal conductivities of three-dimensional silicon, two-dimensional graphene, and a quasi-one-dimensional carbon nanotube and show that the method is about one to two orders of magnitude more efficient than the Green-Kubo method. We apply the spectral decomposition method to examine the long-standing dispute over thermal conductivity convergence vs divergence in carbon nanotubes.