  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 towards 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
analysed 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.
