DELOCALIZATION AND TUNNELING IN THE IONIC STRUCTURE OF LITHIUM MICROCLUSTERS

Quantum effects in the ionic structure of lithium microclusters Li(n) have been estimated by applying a simple Hamiltonian to model selected cluster sizes (n = 20, 40, and 92). Equilibrium structures and thermodynamic properties are computed with use of the path-integral Monte Carlo method. The results show that quantum effects play an important role up to relatively high temperatures. Zero-point motion and tunneling enhance the tendency to disorder already implicit in the delocalized bonding of alkali-metal clusters. The model predicts that, up to the sizes analyzed here, the clusters are fluidlike at all temperatures.