  Recently the occurrence probabilities of ground- and metastable states of
three-dimensional Yukawa clusters with 27 and 31 particles have been analyzed
in dusty plasma experiments [Block et al., Physics of Plasmas 15, 040701
(2008)]. There it was found that, in many cases, the ground state appeared
substantially less frequently than excited states. Here we analyze this
question theoretically by means of molecular dynamics (MD) and Monte Carlo
simulations and an analytical method based on the canonical partition function.
We confirm that metastable states can occur with a significantly higher
probability than the ground state. The results strongly depend on the screening
parameter of the Yukawa interaction and the damping coefficient used in the MD
simulations. The analytical method allows one to gain insight into the
mechanisms being responsible for the occurrence probabilities of metastable
states in strongly correlated finite systems.
