Clusters of Coarse-Grained Water Molecules

Global optimization for molecular
clusters can be significantly
more difficult than for atomic clusters because of the coupling between
orientational and translational degrees of freedom. A coarse-grained
representation of the potential can reduce the complexity of this
problem, while retaining the essential features of the intermolecular
interactions. In this study, we use a basin-hopping algorithm to locate
putative global minima for clusters of coarse-grained water molecules
modeled using a monatomic water potential for cluster sizes 3 ≤ N ≤ 55. We characterize
these structures and identify structural trends using ideas from graph
theory. The agreement with atomistic results and experiment is rather
patchy, which we attribute to the tetrahedral bias in the three-body
potential that results in too few nearest neighbor contacts and premature
emergence of bulk-like structure. In spite of this issue, the results
offer further useful insight into the relationship between the structure
of clusters and bulk phases, and the mathematical form of a widely
used model potential.