ELECTRON-DIFFRACTION STUDIES OF MECHANISMS OF CRYSTAL-STRUCTURE FORMATION IN N-2 CLUSTERS

The structure of N-2 clusters is studied by the electron diffraction m ethod over a wide range of their mean sizes (N) over bar. It is found that, as the value of (N) over bar increases, the structure of the clu sters is transformed in the sequence quasi-crystal (icosahedron) -->al pha-N-2 (cubic) phase with stacking faults -->beta-N-2 (hcp) phase. Th e formation of the cubic phase from the icosahedral structure follows a mechanism typical of rare gases, while the transition alpha-->beta i s due to an increase in the cluster temperature with the size. (C) 199 8 American Institute of Physics.