Comment on "effect of potential energy distribution on the melting of clusters".
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Biomedical subjects
J P Doye
Publications and source records attributed to J P Doye.
Polytetrahedral clusters.
By studying the structures of clusters bound by a model potential that favors polytetrahedral order, we find a previously unknown series of "magic numbers" (i.e., sizes of special stability) whose polytetrahedral structures are characterized by disclination networks that are analogous to hydrocarbons.
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Entropic effects on the size dependence of cluster structure.
We show that the vibrational entropy can play a crucial role in determining the equilibrium structure of clusters by constructing structural phase diagrams showing how the structure depends upon both size and temperature. These phase diagrams are obtained for example rare gas and metal clusters.
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Global optimization and the energy landscapes of Dzugutov clusters.
The global minima of clusters bound by a Dzugutov potential form non-compact polytetrahedral clusters mainly composed of interpenetrating and face-sharing 13-atom icosahedra. As the size increases, these icosahedral units first form linear arrays, then two-dimensional rings, then three-dimensional networks. Characterization of the energy landscapes of these clusters shows that they are particularly rough and generally exhibit a multiple-funnel topography. These results provide new insights into the structure and dynamics of bulk supercooled Dzugutov liquids and the form of the bulk phase diagram.
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Structural relaxation in atomic clusters: master equation dynamics.
The role of the potential energy landscape in determining the relaxation dynamics of model clusters is studied using a master equation. Two types of energy landscape are examined: a single funnel, as exemplified by 13-atom Morse clusters, and the double funnel landscape of the 38-atom Lennard-Jones cluster. Interwell rate constants are calculated using Rice-Ramsperger-Kassel-Marcus theory within the harmonic approximation, but anharmonic model partition functions are also considered. Decreasing the range of the potential in the Morse clusters is shown to hinder relaxation toward the global minimum, and this effect is related to the concomitant changes in the energy landscape. The relaxation modes that emerge from the master equation are interpreted and analyzed to extract interfunnel rate constants for the Lennard-Jones cluster. Since this system is too large for a complete characterization of the energy landscape, the conditions under which the master equation can be applied to a limited database are explored. Connections are made to relaxation processes in proteins and structural glasses.
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Tetrahedral global minimum for the 98-atom Lennard-Jones cluster.
An unusual atomic cluster structure corresponding to the global minimum of the 98-atom Lennard-Jones cluster has been found using a variant of the basin-hopping global optimization algorithm. The structure has tetrahedral symmetry and an energy of -543.665 361 epsilon, which is 0.022 404 epsilon lower than the previous lowest-energy minimum. The LJ(98) structure is of particular interest because its tetrahedral symmetry establishes it as one of only three types of exception to the general pattern of icosahedral structural motifs for optimal LJ microclusters. Similar to the other exceptions the global minimum is difficult to find because it is at the bottom of a narrow funnel that only becomes thermodynamically most stable at low temperature.
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