Cluster analogs of binary isotopic mixtures: Path integral Monte Carlo simulations

The structure of quantum clusters composed of binary isotopic mixtures is studied using Fourier path integral Monte Carlo simulations. Such clusters display a purely quantum analog of the segregation phenomenon observed in classical binary dusters with the lighter isotope preferentially located on the cluster surface and the heavier isotope in the cluster interior. A parametric multistage sampling scheme is developed to equilibrate such quantum mixtures. The behavior of a single isotopic impurity in a quantum cluster is examined as a function of impurity mass, temperature and cluster size. Isotopic segregation effects in mixed para-H-2/ortho-D-2 clusters are shown to be striking. (C) 1996 American Institute of Physics.