| Abstract
| - We have used ab initio methods to study the possible transition between icosahedral (ico) and cuboctahedral(fcc) structures in lead nanoclusters of sizes up to 309 atoms. Spontaneous fcc-to-ico transition in Pb13 wasobserved in the ab initio molecular dynamics (MD) simulations at various temperatures. The transition pathcan be described predominantly by an angular variable s, which can, generally be applied to the similartransitions in clusters of larger sizes and was observed to follow the Mackay model. We have calculated thetwo-dimensional energy surface that describes the transition in Pb13 and found a barrierless fcc-to-ico transitionpath, which is consistent with the observed spontaneous transition in the ab initio MD simulations. The atomicdisplacements in the transition were identified as one of the vibrational eigenmodes of these two Pb13 clusters.For clusters of larger sizes (Pbn, where n = 55, 147, and 309), the possible transitions following similar pathswere determined not to be barrierless and the sizes of the barriers were determined by the ab initio elasticband method.
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