A theoretical investigation on electronic properties and stability of IrSix(x=1-6) clusters

A series of computational investigations on IrSin (n = 1-6) clusters is reported. For each unit, geometry optimizations are performed at the UB3LYP/LanL2DZ level, subsequently, electronic and bonding features of the resulting equilibrium structure are presented and discussed. The emphasis of this study is placed on the geometries, stabilities and electron properties of IrSin (n = 1-6) systems and, more specifically, the impact of the,their spins on the internal electron transfer between the Si-n subsystem and the Ir atom. As a general trend for IrSin clusters with n > 1, we record a change of the natural charge from negative to positive on Ir atom in IrSi and IrSi2 clusters, charges transferring from Si to Ir in IrSi, (n = 3-6) clusters as the spin constraint on the system increases from S = 1/2 to 5/2. This feature is shown to be associated with a pronounced drop in the stability of the IrSin (n not equal 3) clusters as one goes from the doublet to the sextet I spin configurations. It should be mentioned that equilibrium geometries of IrSin (n = 3-6) clusters and ground electron states of IrSi and IrSi3 clusters are obviously different from MSin (M = Cr, Mo, W, Ag, n = 1-6). Our theoretical results show that IrSi2 cluster is the most stable cluster of all IrSin clusters, which is in good agreement with experimental result available. (C) 2002 Elsevier Science B.V. All rights reserved.