Does the Al13- core exist in the Al13 polyhalide Al13I(n)- (n = 1-12) clusters?

We have studied the structures and stabilities of Al(13)I(n) (-)(n = 1-12) clusters at the density-functional level of theory. Unlike the case of Al(13)I(-), the Al(13)I(n) (-)(n=2-12) clusters do not have an Al(13) (-) core electronically. Population analysis shows that a significant charge transfer occurs from the Al cluster to the I atoms, where the populations for Al(13) vary from -0.48(Al(13)I(2) (-)) to +0.97(Al(13)I(12) (-)). Moreover, the shape of Al(13) moieties in the Al(13)I(n) (-) (n > or = 6 or 7) clusters is significantly distorted from the structure of Al(13) (-), an icosahedron, and is a "cagelike" form, which can be explained by both electronic and steric reasons. Our theoretical results are in good agreement with the experimental observations of Bergeron et al. [Science 307, 231 (2005)].