# Size and density sorting of dust grains in SPH simulations of protoplanetary discs

## TL;DR

This study uses 3D SPH simulations to analyze how dust grain size and density influence their vertical and radial distribution in protoplanetary discs, revealing efficient chemical sorting mechanisms relevant to chondrite formation.

## Contribution

It provides a simultaneous analysis of dust size and composition evolution in protoplanetary discs using a novel 3D two-fluid SPH approach.

## Key findings

- Vertical dust settling involves density-driven and size-driven phases.
- Efficient radial chemical sorting occurs at large scales.
- Dust aerodynamical sorting affects inner disc composition and chondrite-like aggregate properties.

## Abstract

The size and density of dust grains determine their response to gas drag in protoplanetary discs. Aerodynamical (size x density) sorting is one of the proposed mechanisms to explain the grain properties and chemical fractionation of chondrites. However, the efficiency of aerodynamical sorting and the location in the disc in which it could occur are still unknown. Although the effects of grain sizes and growth in discs have been widely studied, a simultaneous analysis including dust composition is missing. In this work we present the dynamical evolution and growth of multicomponent dust in a protoplanetary disc using a 3D, two-fluid (gas+dust) Smoothed Particle Hydrodynamics (SPH) code. We find that the dust vertical settling is characterised by two phases: a density-driven phase which leads to a vertical chemical sorting of dust and a size-driven phase which enhances the amount of lighter material in the midplane. We also see an efficient radial chemical sorting of the dust at large scales. We find that dust particles are aerodynamically sorted in the inner disc. The disc becomes sub-solar in its Fe/Si ratio on the surface since the early stage of evolution but sub-solar Fe/Si can be also found in the outer disc-midplane at late stages. Aggregates in the disc mimic the physical and chemical properties of chondrites, suggesting that aerodynamical sorting played an important role in determining their final structure.