Growth of amorphous ice grains by sintering in a protoplanetary disk

An icy grain in a protoplanetary nebula mainly consists of amorphous H 2 O ice and can grow through the migration of H 2 O molecules (sintering). The growth rate through sintering strongly depends on the diffusion constant of H 2 O molecules. I estimated the size of amorphous ice grains as a function of the sintering duration based on the diffusion constant of amorphous ice determined by the molecular dynamics simulation. It has been found that the growth proceeds in a wide disk region ( ∼ 20 AU), and grain can grow to ∼ 1 0 − 3 cm around the snowline. The growth of the icy grains can affect the evolution of the icy dust aggregates in a protoplanetary disk. • Amorphous ice grains can substantially grow by sintering • The region where the grain grows extends to ∼ 20 AU • The evolution of icy dust aggregates might be severely affected.