Scale effects in the nanoscale heat transfer of molecular interfaces with different lattice orientations

Non-equilibrium molecular dynamics simulations were performed in this study to apply a temperature gradient across various embedded atom method (EAM)/EAM solid–solid interfaces with different lattice orientations. The simulation cell size was increased gradually from one unit cell, and we observed that the atomic surface density and volume density fluctuated at the nanometer scale. The density difference between two different crystal orientation grains of the same material fluctuated at the nanometer scale and became constant when the system size became much larger depending on the definition of the boundary. Moreover, the gap between two atomic layers becomes dominant in the calculations of the density of the lattice cell, affecting the grain boundary energy. This gap also affects the interfacial thermal transport for analyses at the nanoscale, and it is crucial to account for this gap during nanoscale thermal transport studies. In this regard, the necessity of considering proper boundary definitions has been discussed in this paper, and we have shown how this consideration affects the interfacial thermal transport analysis.