Screening-controlled morphologies of Yukawa crystals.
Asymptotic expressions for the energies of Yukawa crystals, valid at the Coulomb and hard-sphere (i.e., the weak-screening and strong-screening) limits, are derived. Careful analysis of these limits elucidates the origin of the observed structural transitions that interconnect distinct particle configurations. Whereas the Coulomb limits are characterized by prominent shell structures, their hard-sphere counterparts obtain from tight packings of impenetrable spheres that minimize radii of gyration. Interestingly, these packings are not identical with fragments of regular close-packing lattices. In crystals of more than seven particles, the limiting configurations usually possess distinct point-group symmetries and thus are mutually incompatible. This incompatibility constitutes the driving force for the structural transitions and precludes smooth interpolation of the energies in question. As demonstrated by the examples of the eight- and eleven-particle species, the overall picture of structural transitions (which involve either catastrophes or level crossings) and Yukawa crystal morphologies is much more complex than that revealed by monitoring of shell occupancies alone.
Cioslowski
Jerzy
J
Institute of Physics, University of Szczecin, Wielkopolska 15, 70-451 Szczecin, Poland. jerzy@wmf.univ.szczecin.pl
Grzebielucha
Ewa
E
D003460:Crystallization; D008956:Models, Chemical; D010316:Particle Size; D013816:Thermodynamics