Skip to main content
SearchLoginLogin or Signup

Simulating dust monomer interaction

Presentation #615.14 in the session Planet Formation Theory.

Published onApr 03, 2024
Simulating dust monomer interaction

Collisional sticking is the first process of dust aggregate growth, while the fragmentation barrier prohibits the growth of dust aggregates. When the dust aggregates collide at high velocities of several tens m/s, they are broken and become fragments. The maximum collisional velocity can reach 50 m/s in the protoplanetary disks (e.g., Adachi et al. 1976; Weidenschilling & Cuzzi 1993). To discuss this problem, we should understand the critical collision velocity of fragmentation, and many numerical simulations of dust aggregate collisions have been performed (e.g., Wada et al. 2007, 2008, 2009, 2013; Suyama et al. 2008, 2012). Dust aggregates are composed of many submicron-sized particles, called monomers. Numerical simulations of dust aggregate collisions are monomers’ N-body problems in which interactions between monomers in contact are calculated based on the JKR theory, which is one of the contact models. However, the JKR theory doesn’t consider molecular effects such as molecular motions and deformation of monomers. It is suggested that they lead to energy dissipation at collisions and promote coalescence (Krijt et al. 2013; Tanaka et al. 2012). Therefore, the monomer interaction should be investigated, including molecular physics. We perform molecular dynamics (MD) simulations to investigate the interaction between monomers. First, we simulate head-on collisions of monomers to investigate the coefficient of restitution (COR) and its dependence on monomer radius (10-100 nm), impact velocity (20-150 m/s), and temperature (0-80 K). As a result, we find that the COR of the MD simulations is smaller than that of the JKR theory. Surprisingly, The COR decreases for the impact velocity larger than 50 m/s due to monomer deformation. We also find that the COR decreases with increasing temperatures. At high temperature monomers are softer, which leads to larger energy dissipation. Next, we simulate rotating monomers in contact to investigate the rolling interaction. We calculate the resistive torque acting between monomers. The time evolution of the angular velocity of a monomer gives the torque. We find that the angular velocities of both monomers first decrease linearly, and then oscillate with approaching zero. The damped oscillation is not included in the previous rolling model (Dominik & Tielens 1995). We will present the above results.

No comments here