Determination of structural transitions of atomic clusters from local and global bond orientational order parameters

Designing an effective order parameter for the identification of geometries in atomic clusters is an important step toward understanding the structural transitions occurring in these systems. We propose a method that simultaneously utilizes the local and global bond orientational order parameters for structural transitions. When applied to Lennard-Jones clusters at finite temperature over the size range 30 <= N <= 146, this method identified all the major geometries: icosahedra with Mackay overlayers, icosahedra with anti-Mackay overlayers, decahedra, octahedra, and tetrahedra. From the distributions of these geometries as a function of temperatures on clusters containing 38, 75, and 98 atoms, we are able to interpret all transition types without ambiguity. (c) 2007 American Institute of Physics.