Novel Lattice-Searching Method for Modeling the Optimal Strain-Free Close-Packed Isomers of Clusters

Small icosahedral, decahedral, and fcc structures have been studied by unbiased global optimization methods
or Wulff construction and Northby lattice methods. Strain-free close-packed structures are not much discussed
because the structures are very difficult to optimize and there is no common strain-free close-packed lattice.
We propose a new strategy to construct such a lattice containing all possible strain-free close-packed isomers,
and by searching the lattice with an efficient method the optimal close-packed structures were modeled.
Testing with the Morse potential at ρ0 = 14.0 for cluster size 10 ≤ N ≤ 250 showed that optimal strain-free
close-packed (scp) structures are lower in energy than fcc structures in most cases even for the well-known
magic numbers of fcc structures (e.g., N = 201). It was found that, due to the gaps in next-nearest-neighbor
contacts, fcc will become energetically incomparable with scp at very large clusters with a pair potential.
Moreover, compared with the results in the literature, some new global minima for Morse clusters at large ρ0
values are given.