Molecular dynamics simulation of thermal accommodation coefficients for laser-induced incandescence sizing of nickel particles

Extending time-resolved laser-induced incandescence (TiRe-LII), a diagnostic traditionally used to characterize soot and other carbonaceous particles, into a tool for measuring metal nanoparticles requires knowledge of the thermal accommodation coefficient for those systems. This parameter can be calculated using molecular dynamics (MD) simulations provided the interatomic potential is known between the gas molecule and surface atoms, but this is not often the case for many gas/surface combinations. In this instance, researchers often resort to the Lorentz-Berthelot combination rules to estimate the gas/surface potential using parameters derived for homogeneous systems. This paper compares this methodology with a more accurate approach based on ab initio derived potentials to estimate the thermal accommodation coefficient for laser-energized nickel nanoparticles in argon. Results show that the Lorentz-Berthelot combining rules overestimate the true potential well depth by an order of magnitude, resulting in perfect thermal accommodation, whereas the more accurate ab initio derived potential predicts an accommodation coefficient in excellent agreement with experimentally-determined values for other metal nanoparticle aerosols. This result highlights the importance of accurately characterizing the gas/surface potential when using MD to estimate thermal accommodation coefficients for TiRe-LII.