Coarse-Grained Models of Nanocluster Interaction Potentials: Application to Metal, Organic, and Carbon Materials

JOSÉ MORÁN, Christopher J. Hogan, University of Ottawa

     Abstract Number: 634
     Working Group: Aerosol Physics

Abstract
Trajectories and collision frequencies of nanoparticles in gas-phase are highly dependent on their interaction potentials including Coulomb and van der Waals (vdW). The latter can be complex to model and is commonly neglected in numerical simulations based on meso-scale or sectional approaches. Some approaches exist in the literature including the Hamaker’s equation (Hamaker, 1937) to predict vdW interactions between spherical particles and its extension to the repulsive short-range potentials (Lazaridis and Drossinos, 1998). However, these models are not accurate for metal, metal-oxides or organic nanomaterials due to multi-body effects and free electrons in the case of metals. This holds true regardless of the method used to calculate the material Hamaker’s constant including complex approaches such as the Lifshitz theory. This is shown here based on all-atoms molecular dynamics simulations using LAMMPS (Thompson et al., 2022) to model carbon, silica, and gold nanoclusters. Based on these simulations, we have proposed a new model to coarse-grain the interaction potentials between nanoclusters and validated our model’s accuracy to predict a vdW coagulation enhancement of aerosol particles in the diffusive and ballistic regimes. The latter is done by comparison of such enhancement coefficients as a function of the nanocluster size obtained from both all-atoms and coarse-grained simulations. The new equation could be used in future numerical simulations including meso-scale or sectional where a vdW coagulation enhancement is important including the aerosol synthesis of nanomaterials in flames or plasma systems.

Hamaker, H. C. (1937). The London—van der Waals attraction between spherical particles. physica, 4(10), 1058-1072.
Lazaridis, M., & Drossinos, Y. (1998). Multilayer resuspension of small identical particles by turbulent flow. Aerosol Science and Technology, 28(6), 548-560.
Thompson, A. P., Aktulga, H. M., Berger, R., Bolintineanu, D. S., et al. (2022). LAMMPS-a flexible simulation tool for particle-based materials modeling at the atomic, meso, and continuum scales. Computer physics communications, 271, 108171.