Quantum bath augmented stochastic nonequilibrium atomistic simulations for molecular heat conduction

Renai Chen; Mohammadhasan Dinpajooh; Abraham Nitzan

doi:10.1063/5.0168117

Quantum bath augmented stochastic nonequilibrium atomistic simulations for molecular heat conduction

J Chem Phys. 2023 Oct 7;159(13):134110. doi: 10.1063/5.0168117.

Authors

Renai Chen^{1

2}, Mohammadhasan Dinpajooh³, Abraham Nitzan^{1

4}

Affiliations

¹ Department of Chemistry, University of Pennsylvania, Philadelphia, Pennsylvania 19104, USA.
² Theoretical Division and Center for Nonlinear Studies, Los Alamos National Laboratory, Los Alamos, New Mexico 87544, USA.
³ Physical and Computational Sciences Directorate, Pacific Northwest National Laboratory, Richland, Washington 99352, USA.
⁴ School of Chemistry, Tel Aviv University, Tel Aviv 69978, Israel.

PMID: 37800644
DOI: 10.1063/5.0168117

Abstract

Classical molecular dynamics (MD) has been shown to be effective in simulating heat conduction in certain molecular junctions since it inherently takes into account some essential methodological components which are lacking in the quantum Landauer-type transport model, such as many-body full force-field interactions, anharmonicity effects and nonlinear responses for large temperature biases. However, the classical MD reaches its limit in the environments where the quantum effects are significant (e.g. with low-temperatures substrates, presence of extremely high frequency molecular modes). Here, we present an atomistic simulation methodology for molecular heat conduction that incorporates the quantum Bose-Einstein statistics into an "effective temperature" in the form of a modified Langevin equation. We show that the results from such a quasi-classical effective temperature MD method deviates drastically when the baths temperature approaches zero from classical MD simulations and the results converge to the classical ones when the bath approaches the high-temperature limit, which makes the method suitable for full temperature range. In addition, we show that our quasi-classical thermal transport method can be used to model the conducting substrate layout and molecular composition (e.g. anharmonicities, high-frequency modes). Anharmonic models are explicitly simulated via the Morse potential and compared to pure harmonic interactions to show the effects of anharmonicities under quantum colored bath setups. Finally, the chain length dependence of heat conduction is examined for one-dimensional polymer chains placed in between quantum augmented baths.