Semi-quantum approach to molecular dynamics simulation of thermal properties of low-dimensional nanostructures

TL;DR

This paper introduces a semi-quantum molecular dynamics method that incorporates quantum phonon effects into classical simulations, enabling accurate modeling of thermal properties in low-dimensional nanostructures across a range of temperatures.

Contribution

The paper develops a semi-quantum approach using colored noise in molecular dynamics to simulate quantum phonon effects in thermal transport of nanostructures.

Findings

Quantum phonon effects significantly influence specific heat and thermal conductivity of carbon nanotubes below 500K.

The method accurately determines temperature from vibrational spectra without classical equipartition.

Thermal transport varies with edge roughness and anharmonicity in nanoribbons.

Abstract

We present a detailed description of semi-quantum molecular dynamics simulation of stochastic dynamics of a system of interacting particles. Within this approach, the dynamics of the system is described with the use of classical Newtonian equations of motion in which the effects of phonon quantum statistics are introduced through random Langevin-like forces with a specific power spectral density (the color noise). The color noise describes the interaction of the molecular system with the thermostat. We apply this technique to the simulation of thermal properties and heat transport in different low-dimensional nanostructures. We describe the determination of temperature in quantum lattice systems, to which the equipartition limit is not applied. We show that one can determine the temperature of such system from the measured power spectrum and temperature- and relaxation-rate-independent density of vibrational (phonon) states. We simulate the specific heat and heat transport in carbon nanotubes, as well as the heat transport in molecular nanoribbons with perfect (atomically smooth) and rough (porous) edges, and in nanoribbons with strongly anharmonic periodic interatomic potentials. We show that the effects of quantum statistics of phonons are essential for the carbon nanotube in the whole temperature range T<500K, in which the values of the specific heat and thermal conductivity of the nanotube are considerably less than that obtained within the description based on classical statistics of phonons.