Formation and fragmentation of the tungsten clusters in gas phase.

We present a theoretical study of accumulation of clusters consisting of up to 100 tungsten atoms based on information extracted from molecular dynamics trajectory simulations. The description is based on the rates corresponding to the single W atom attachment to W_n clusters and their dissociation processes. The results display a strong Arrhenius dependence of the dissociation rate constant on temperature. The preferred products of dissociation of the clusters composed of more than ten atoms are single W atoms and fragments with six to nine atoms. On the other hand, the association rate constants depend weakly on temperature. The obtained rate constants are used to calculate the chemical equilibrium of the W clusters that results in significant traces of small clusters only at high initial W atoms concentrations. [ABSTRACT FROM AUTHOR]