Formation and properties of astrophysical carbonaceous dust

Abstract The classical theory of grain nucleation suffers from both theoretical and predictive deficiencies. We strive to alleviate these deficiencies in our understanding of dust formation and growth by utilizing an atomistic model of nucleation. Carbon cluster geometries are determined with a set of global minimization algorithms. Using density functional theory, the binding energies of carbon clusters from n =2 to n =99 are then calculated. These energies are used to calculate the critical size and nucleation rate of carbon clusters. We find that the critical cluster size is largely determined by the changes in geometry of the clusters. Clusters with size n =27 and n =8, roughly corresponding to the transition from ring-to-fullerene geometry and chain-to-ring geometry respectively, are the critical sizes across the range of temperature and saturation where nucleation is significant. In contrast to the classical theory, nucleation is enhanced at low-temperatures, and suppressed at high temperatures. These results will be applied to a modified chemical evolution code using results from supernova simulations.