Molecular Dynamics Simulations Explore Dust Monomer Interactions: An Extension of the JKR Adhesion Model
speaker: Yuki Yoshida
Abstract:
Dust is the main material of planets, and grows into planets. The minimum unit of dust is considered to be a sphere 0.1 um in size called a monomer. Monomers grow to cm size by collisional coalescence due to intermolecular forces. However, the growth process is not understood well. The collisional growth process has been studied by laboratory experiments and numerical calculations. In numerical calculations, the JKR theory, which gives the interactions of adhesion, rotation, sliding, and twisting between monomers, is used as the monomer interaction. However, it has been suggested that actual monomers have viscosity so that a part of the kinetic energy of the monomers is converted to that of the molecules (Tanaka et al. 2015). Therefore, it is necessary to extend the JKR theory based on molecular physics.We investigated monomer head-on collision to clarify the adhesion interactions by performing molecular dynamics (MD) simulations and investigated the coeffecient of restitution. We then performed simulations with temperatures and impact velocities to obtain the dependence on the coeffecient of restitution. In this talk, I will present our MD simulation and our recent studies. We found that the coefficient of restitution decreases when the impact velocity is higher than a certain value or when the temperature is higher. In addition, the coefficient of restitution is significantly smaller for higher impact velocity compared to the JKR theory, indicating that collisional physics and the JKR theory are qualitatively different. We, therefore, attempted to modify the JKR theory using the dissipative model of Krijt et al. (2013). We will present these results in detail and propose a new extended theory of JKR theory.