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Abstract

When molecular clouds collapse to form stars, protoplanetary disks consisting of gas and dust are often formed as byproducts of star formation. It is assumed that planets are built from this leftover gas and dust in these disks by collisional growth of dust particles and subsequent accretion of gas. The exact mechanism, however, is not well understood. Protoplanetary disks, in general, have temperature profiles with decreasing temperatures with increasing distances from the star. At the location, where the temperature drops below the condensation temperature of a volatile molecular species – the ice line –, the volatile freezes out as ice. This changes the chemical composition of the dust particles depending on their location in the disk. The composition of planets and planetesimals, that are formed from the dust in these disk, is therefore depending on their formation locations relative to the ice lines. We developed a model to investigate the transport of volatile molecular species in protoplanetary disks including dust coagulation and transport, gas advection and diffusion, and evaporation and condensation of volatiles. We found that particles shortly outside of ice lines are enriched in the respective volatile species due to backward diffusion and recondensation of vapor. This recondensation has also a direct effect on the coagulation physics of the dust particles and can create ring-like, axis-symmetric dust features in protoplanetary disks.