Density functional theory with the generalized gradient approximation was used to determine the geometries, energies, transition states, and vibrational frequencies of the [AlCl]n(n=1-10) clusters that form during the production of aluminum by the carbothermic reduction-disproportionation reaction. The ground state and trends observed during the formation of [AlCl]n were confirmed. Results indicate that the ground state geometric configurations of the [AlCl]n(n=1-10) clusters are frameworks of [Al]n bound to n Cl atoms and they have excellent geometric symmetry. Activation energies obtained from transition state calculations indicate that the activation energy of the reverse process is always higher than that of the forward process. This means that AlCl tends to form [AlCl]n. Our results can help in the understanding of this aluminumproduction mechanismduring the carbothermic reduction-disproportionation reaction.