DUST FORMATION IN STELLAR WINDS .6. MOMENT EQUATIONS FOR THE FORMATION OF HETEROGENEOUS AND CORE-MANTLE GRAINS

The grains found in interstellar and interplanetary space are well kno wn to often be of amorphous heterogeneous structure. Nevertheless a qu antitative theory for the description of the growth of these particles is still missing. We show that the well known moment method for the c alculation of dust grain formation can be generalized in order to acco unt also for the formation of heterogeneous dust grains. These include both grains consisting of a mixture of different molecules and the so -called core-mantle grains where different materials condense in layer s on the grains. Furthermore we construct a special equilibrium state that allows for the calculation of equilibrium densities of various mo lecules above composite grain materials. The new equations are applied to dust condensation in the wind of an M giant star.