Towards more accurate molecular dynamics calculation of thermal conductivity: Case study of GaN bulk crystals

Abstract

Significant differences exist among literature for thermal conductivity of various systems computed using molecular dynamics simulation. In some cases, unphysical results, for example, negative thermal conductivity, have been found. Using GaN as an example case and the direct non-* X. W. Zhou: xzhou@sandia.gov Both the direct and Green-Kubo approaches require long simulations (e.g. at least 1 ns) to reduce the uncertainty due to thermal fluctuations. For the direct method, another difficulty encountered is that the computed thermal conductivity depends strongly on the system length L along the propagation direction, which is typically limited to at most a few hundred nanometers. This means that for perfect bulk crystals the phonon mean free path is comparable to the system size and transport occurs in a partially ballistic regime [17,18,[21][22][23]. It follows from kinetic theory that the computed values of κ are smaller than that of a true bulk system. To obtain values that can be meaningfully compared with experiments, it is therefore necessary to perform several simulations for different cell lengths, and then

Thermal Conductivity of Periclase (MgO) from First Principles

“…A recent study finds close adherence to Eq. (4) with deviations from linearity producing biases in the value of k 1 that are small compared to the uncertainty in our simulations [16].…”

Relationship of thermal boundary conductance to structure from an analytical model plus molecular dynamics simulations

“…Our previous molecular dynamics simulations on thermal transport in GaN 51,55,56 have applied the GaN StillingerWeber (SW) potential 38 parameterized by Béré and Serra 70,71 . To generate a consistent set of data, the same GaN potential is used in the present study to model the semiconductor layer.…”

“…Although 300 K is at the lower bound of the estimated Debye temperature range, we emphasize again that our objective is not to extract quantitative data for specific materials but rather to discover functional dependence of Kapitza conductance on interfacial structures. The low temperature MD simulations are beneficial for such studies as they effective reduce systematic / statistic errors 51,55,56 , which is the limiting factor for discovering accurate functional dependences.…”

Anisotropic thermal conductivity in uranium dioxide

“…In the directions perpendicular to the thermal current, the simulation cells have lengths ranging from 3.7 to 4.0 nm. The dependence of the computed thermal conductivity on cross-sectional area has been shown to be weak 34 . However, for UO 2 , the dimensions of the simulation cell impact the ellipsoidal character of the projected oxygen trajectory illustrated in Fig.…”