Nonequilirium Molecular Dynamics Methods for Lattice Heat Conduction Calculations

Abstract

Over the last decades, molecular dynamics simulations have been extensively used to calculate lattice heat conduction in nano-and bulk-materials, as the realistic potential functions, software package, and many core clusters have become widely accessible. Nonequilibrium molecular dynamics, particularly the inhomogeneous ones, have been a popular choice of method owing to their intuitive way of applying the perturbation to the system. On the other hand, despite its simplicity, the results can be significantly influenced by the simulation parameters, and various methodological issues such as validity of linear response theory, effect of sizes, influence of temperature or heat flux control need to be carefully checked and taken into account. These aspects are discussed for various types of nonequilibrium methods based on homogeneous/inhomogeneous and steady/transient molecular dynamics simulations. Their capability to calculate bulk thermal conductivity, heat wave propagation, the classical size effect of thermal conductivity at the nanoscale, and total and spectral thermal boundary conductance are explained and demonstrated with examples. NOMENCLATURE Acronyms CNT carbon nanotube EMD equilibrium molecular dynamics DFT density functional theory GK Green-Kubo GROMACS Groningen machine for chemical simulations Φ harmonic interatomic force constant [Nm-1 ]  cubic interatomic force constant [Nm-1 ] X quartic interatomic force constant [Nm-1 ]

Lattice thermal conductivity of graphene nanostructures

“…We have also tried an alternative method of the conductivity calculation, consisting in maintaining a fixed temperature difference between the contacts and calculating the energy flux. In this case temperature profiles can be highly nonlinear, characterized by abrupt temperature changes at the contacts (resulting from a mismatch between the dispersion relation of the fixed temperature parts and the rest of the system [55]). To avoid the non-physical temperature kinks, larger contacts have to be considered increasing the simulation time considerably, for which reason the latter approach was abandoned.…”

Quantitatively analyzing phonon spectral contribution of thermal conductivity based on nonequilibrium molecular dynamics simulations. I. From space Fourier transform

“…VI A. It is also worth noting that the characteristic size is more accurate and easier to be found when the control volume is 24 larger, since more phonon modes can be extracted in TDDDM run. Another interesting result is that the characteristic size identified in TDDDM is more or less equal to the total size of the simulation system, i.e.…”

Phonon Transport and Thermal Conductivity in Two-Dimensional Materials

“…In MD simulations, the movements of atoms within a small computational domain are simulated and recorded according to Newton's second law. Both non-equilibrium molecular dynamics (NEMD) [68] and equilibrium molecular dynamics (EMD) [69] have been developed to calculate thermal conductivity of bulk, nanostructured and 2D materials. In NEMD, heat flux is applied by inserting/removing energy into/out of the system.…”