From molecular clusters to bulk matter. II. Crossover from icosahedral to crystalline structures in CO_2 clusters

摘要

The change in structure with size in (CO_2)_N clusters has been investigated in the crossover regime from icosahedral to cubic morphology (N = 19 to 55) by molecular dynamics simulation. All the minima in the potential energy surface (PES) visited by the solid clusters at finite temperature have been characterized using a local structure analysis method. A simple picture of the change in free-energy minimum with size in CO_2 solid clusters emerges from this work. It is based on the relative stability of two energy basins in the PES corresponding to the icosahedral and cubic-like structure, respectively. In addition, some evidence is provided for the existence of an icosahedral supercooled liquid in the size range near N approx 50.