Theoretical analysis of 17-19-atom metal clusters using many-body potentials

A detailed study is presented of the low-energy isomers for 17-19-atom clusters of Al, Ca, Fe, Ni, Pd and Pt, bound by Murrell-Mottram 2 + 3-body potentials, using a Random Search method. A systematic analysis is also made of isomers formed by removing one or two atoms from the double icosahedron M₁₉ cluster geometry. Such "incomplete double icosahedra" are predicted to be the global minima for Pd₁₈, Fe₁₈ and Ca₁₈-although the global minima for Fe₁₈ and Ca₁₈ are different to those previously described. In the cases of Al, Ni and Pt clusters, there are low-lying isomers (or even global minima) which are not derived from the double icosahedron, but rather have four-fold symmetry structures derived from capped Ino decahedra. Comparisons are made between the results obtained for Murrell-Mottram potentials and alternative many-body (Sutton-Chen) and pair (Lennard-Jones and Morse) potentials. Similar structural patterns are observed and differences are found between the various elements for both the Murrell-Mottram and the Sutton-Chen potentials.