Molecular Dynamics Simulation of Thermal Accommodation Coefficients for Laser-Induced Incandescence Sizing of Nickel Nanoparticles

Abstract

While time-resolved laser-induced incandescence is most often used to characterize the size and concentration of aerosolized carbonaceous particles, it has recently been applied to aerosols containing metal nanoparticles. This calculation requires the thermal accommodation coefficient, however, which is often difficult to determine experimentally. This paper presents a molecular dynamics investigation of the thermal accommodation coefficient between laser-energized nickel nanoparticles immersed in argon, and the underlying the gas-surface scattering physics. The predicted interaction between gas molecules and the laser-energized surface depends strongly on the potential between the gas molecule and a surface atom: a Lennard-Jones 6–12 potential derived using the Lorentz-Berthelot combination rules overestimates the potential well due to a bond-order effect in the nickel, resulting in strong trapping-desorption and near-perfect thermal accommodation. A Morse potential with parameters obtained directly from ab initio free energies predicts a relatively brief interaction between the gas molecule and nickel surface, on the other hand, and a lower thermal accommodation coefficient similar to experimentally-derived values for laser-energized iron nanoparticles in argon reported in the literature.