Coagulation of grains and gas-grain interactions.

Three-dimensional off-lattice Monte Carlo simulations have been used to simulate the production of interstellar dust analogues on the computer. At first, the two rather well known extreme cases of ballistic growth, i.e. particle-cluster (BPCA) and cluster-cluster aggregation (BCCA) were investigated. In a second step, we included rotation of the clusters during the growth process. Following this, gas particles were deposited on these aggregates taking variable sticking probabilities due to the growth of monolayers into account. This is of interest to the problem of molecular abundances in dark clouds.