Kavli Affiliate: Lile Wang
| First 5 Authors: Sheng Xu, Sheng Xu, , ,
| Summary:
The inner regions of protoplanetary disks are host to the sublimation of dust
grains, a process traditionally modeled using equilibrium thermodynamics. We
demonstrate through ab-initio density functional theory (DFT) and kinetic Monte
Carlo (KMC) simulations that silicate dust sublimation is inherently a
non-equilibrium kinetic process. The binding energies and vibrational
frequencies governing desorption, calculated for MgSiO3 and other compositions,
reveal that sublimation timescales far exceed local dynamical times, allowing
grains to persist in a superheated state. This kinetic inhibition results in a
broad, dynamic sublimation front whose location and morphology are strongly
regulated by radial advection and dust coagulation. Our coupled simulations,
integrating sublimation with advection and grain evolution, show that the front
varies radially by a factor of four with accretion rate and exhibits a
vertically stratified, bowl-shaped structure. These findings imply that the
inner disk dust distribution, thermal structure, and subsequent planet
formation are profoundly influenced by the kinematics and kinetics of dust
grains, necessitating a departure from equilibrium prescriptions in disk models
and interpretations of inner rim observations.
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