In situ surface electron energy loss fine structure investigations of copper clusters deposited on pyrolytic boron nitride

Copper clusters were prepared by using the inert gas aggregation technique. In situ surface electron energy loss fine structure investigations above the M2,3 edge show a sizeable dilatation of the first nearest-neighbour distance provided the mean diameter of the clusters is decreased to 40 Å (corresponding to a number N0 in the cluster of approximately 2800 atoms). Below this value our results are in good agreement with the predicted contraction according to the liquid drop model. The latter, however, strongly contradicts the results recently found using high resolution transmission electron microscopy and electron diffraction. It is believed that this contraction can be explained by inharmonic surface crystal potentials for small particles