  The heat capacity and isomer distributions of the 38 atom Lennard-Jones
cluster have been calculated in the canonical ensemble using parallel tempering
Monte Carlo methods. A distinct region of temperature is identified that
corresponds to equilibrium between the global minimum structure and the
icosahedral basin of structures. This region of temperatures occurs below the
melting peak of the heat capacity and is accompanied by a peak in the
derivative of the heat capacity with temperature. Parallel tempering is shown
to introduce correlations between results at different temperatures. A
discussion is given that compares parallel tempering with other related
approaches that ensure ergodic simulations.
