DYNAMICS OF FORMATION AND EVAPORATION OF MIXED-ALKALI HALIDE NANOCRYSTALS - A CASE OF COMPARABLE LATTICE ENERGIES

The relative intensity distribution of the [Rb,K14-nI13](+) mixed nano crystals containing a ''magic'' number of 14 metal cations and 13 iodi de anions is examined. These nanocrystals were generated through sputt ering of mixed RbI/KI solids using fast atom bombardment and analyzed by use of a double-focusing sector-field mass spectrometer. The relati ve intensities of the observed peaks are found to have a ''bimodal'' d istribution with a maximum near n = 7. This observation is explained b y assuming: (a) a rate of formation that is proportional to the number of isomers that can be formed for each mixed nanocrystal, and (b) a r ate of dissociation that is insensitive to the composition of the mixe d nanocrystal. The later assumption leads to the conclusion that the i nternal energies of these mixed nanocrystals are similar and independe nt of their composition. This conclusion is supported by the results o f Monte Carlo simulation annealing as well as by the similarity of the known lattice energies of KI and RbI bulk crystals.