ELECTRON-DIFFRACTION STUDY ON THE RISE OF CRYSTAL PHASE IN RARE-GAS AND NITROGEN CLUSTERS

The structure of Ar-N Kr-N Xe-N and (N-2)(N) clusters are studied by t he electron diffraction method in a wide range of mean sizes (N) over bar. It is found that rare-gas clusters of mean sizes (N) over bar gre ater than or equal to 2000 atoms/cluster have a fee structure with the ''deformation''-type stacking faults. It is found that in the case of nitrogen clusters as N increases the cluster structure transforms in the sequence: quasi-crystal (icosahedron) --> alpha (cubic) phase --> beta (hcp) phase. The formation of the cubic phase from the icosahedra l structure follows the mechanism typical of rare gases. The transitio n alpha --> beta is due to the increase of the cluster temperature wit h size. The results obtained support the theoretical hypothesis on the important role of the kinetic factor in the formation of atomic clust er structures. (C) 1998 Elsevier Science B.V. All rights reserved.