LAUSR

Abstract  We have employed an evolutionary algorithm (EA) to study the low-energy landscape of clusters modeled with a potential which is composed by an attractive Morse function and a repulsive Yukawa component. Since the range of the Morse potential is controlled by a single parameter ( ρ ), this has been varied between 3 and 14 to study its influence on the lowest-energy structure. The present results show that shorter-ranged attractive potentials tend to magnify the effect of the repulsive Yukawa function on the global minimum structure. Due to the higher energy-barriers, the short-range attractive interactions produce low-energy dissociated structures at smaller cluster sizes than long-range potentials. As a consequence of this, global minimum structures of clusters involving short-range attractive potentials tend to be elongated in order to reduce the number of second nearest-neighbor particles that usually correspond to a very repulsive contribution for the interaction energy. In addition, Bernal spirals and beaded-necklace motifs are often observed for potentials with a short-range attractive component, while long-ranged interactions can hardly support such structures. We have also searched for the global minima of the N = 13 binary clusters formed by various combinations of the ρ -parameter in the Morse potential. Most of such binary clusters are unstable in relation to the corresponding N = 13 homogeneous aggregates, and the structure tend to assume the usual icosahedral shape (especially for the cases involving the longer-range potentials) with particles associated to lower ρ -values preferentially located on the surface.