Structural transition in rare earth oxide clusters

摘要

Size effects,such as structure transition,have been reported in small clusters of alkali halide compounds.We extend the study to rare earth sesquioxide (Gd_2O_3) clusters which are as ionic as the alkali halide compounds,but have a more complicated structure.In a clean and controlled environment (ultra high vacuum),such particles are well crystallized,facetted and tend to adopt a rhombic dodecahedron shape.This indicates the major role of highly ionic bonds in preserving the crystal lattice even at small sizes (a few lattice parameter).Based on both cathodo-luminescence and transmission electron microscopy,we report the existence of a structural transition from bcc to monoclinic at small sizes.