SIMULATION OF STRUCTURE, DYNAMICS AND ELECTRON DIFFRACTION PATTERNS OF HETEROGENEOUS CLUSTERS: Arm(N2)n

The nitrogen-argon system provides a useful paradigm for studying segre-gation and mixing behavior in heterogeneous clusters. Using three realistic pair potentials corresponding to argon-argon, nitrogen-nitrogen and argon-nitrogen in-teractions, the structures and thermodynamics of Arm (N2), clusters are investi-gated. Comparison of these results to previous simulation results on neat argon and nitrogen clusters is made. The initial focus of the study is the series of thirteen particle clusters of Arm(N2)13-m (0 5 m 5 13); molecular dynamics in the microcanonical ensemble is the principle simulation tool. The icosahedral nitrogen-argon clusters display systematic changes in energetics when argon is substituted by nitrogen in the cen-tral position. Comparisons between argon centered and nitrogen centered clusters are made. The consequences of these observations for cluster stability and for dy-namical behavior, such as melting and evaporation, are investigated. These results are interpreted in terms of frustration effects due to anisotropy in the N2-N2 and N2-Ar potentials. Study of larger clusters reveals that the argon core clusters ar