EFFECTS OF SOLID/FLUID BOUNDARY DEFINITION ON ESTIMATING NANOSCALE PHENOMENA: A MOLECULAR DYNAMICS STUDY

Abstract

In this work, we investigate the atomic-level wall/fluid boundary to properly analyze nanochannel heat transfer using molecular dynamics (MD) simulations. In the absence of an atomic-level boundary definition, the wall/fluid boundary has been differently defined within one atomic diameter. This amount of discrepancy of boundary definition can cause significant impacts on the computed observables in small scale. To clarify these impacts, we conducted heat transfer MD simulations of liquid argon confined between two silver walls. The fluid density, heat flux across the channel, and the fluid thermal conductivity were calculated with respect to the different definitions of wall/fluid boundary. Our results reveal that one atomic diameter boundary shift causes relatively large deviations between the computed and the preset values. In addition, these variations become more significant as the channel height decreases. It is shown that the uncertainty atomic-level boundary definition can create not only a quantitative but also qualitative discrepancy. We also specify wall/fluid boundary in atomic accuracy using microscopic heat flux equation. The location shows a good agreement with literature and zero-potential location of wall molecule where is the wall boundary at absolute zero temperature. The findings in this work provide atomic-level insights into the wall/fluid boundary, as well as useful information on the design of nano-devices aimed at energy optimization.