Abstract View
Calculation of the Nanoparticle-Ion Attractive Collision Rate Coefficient by Continuum-Molecular Dynamics Hybrid Simulations
TOMOYA TAMADATE, Takafumi Seto, Christopher J. Hogan, University of Minnesota
Abstract Number: 8
Working Group: Aerosol Physics
Abstract
Nanoparticle charging plays an important role in numerous aerosol measurement applications; for example, the charge distribution is often needed a priori in size distribution inversion from mobility distributions. Charge distributions are usually not measured directly, and are instead estimated from ion-particle collision limited reaction models, which are dependent upon the ion-particle collision rate coefficient. While regression equations for the charge distribution based upon a modified version of Fuchs limiting sphere model are almost universally applied in aerosol measurement, these equations have not been rigorously tested for nanoclusters (1-2 nm particles) and recent work suggests they may not be accurate specifically for collisions between nanoclusters and ions of opposite charge. Recently, we developed a “continuum-molecular dynamics simulation hybrid approach”, to determine ion-ion recombination rates. This method is based on the limiting sphere method classically used for transition regime collision phenomena in aerosols, but utilizes molecular dynamics simulation with all-atom models within the limiting sphere. Here, we extend this method to examine nanocluster-ion collisions, specifically for positively charged argon and negatively charged silicon nanocluster composed of 50 to 500 atoms (1 to 3 nm), with changing pressure (102 to 105 Pa) and different two temperatures (300 and 1,000 K). Results are compared to the classical limiting sphere method, as well as recently developed collision rate coefficients for ion-particle systems.