Investigation of morphology of an enneadic particle system confined onto a spherical surface through Monte Carlo...

The morphology of an enneadic particle system confined to a spherical surface is investigated through Monte Carlo simulation. The model assumes nine hard spheres adsorbed onto a spherical surface of the same diameter. In addition to hard core repulsion, these nine particles interact through Coulomb repulsion or Lennard-Jones potential. At a low enough temperature, the ordered structure of the enneadic particle system exhibits a symmetric arrangement corresponding to the D(3h) point group and is similar to hexagonal close packing. The nine particles can be divided into three groups, and each group occupies an equilateral triangle along with the same principle axis. The top and bottom triangles form the mirror image and the middle triangle of a different size rotates 60 degrees from the other two triangles. This symmetry is independent of interaction potentials but the two interaction potentials deform the ordered structure in a slightly different way. From the analysis of monomers of inertia, we notice that Coulombic particles compress the ordered morphology to an oblate shape, whereas Lennard-Jones particles display an elongated prolate morphology. By use of the analysis of a simple model, we find that these fine structures tend to lower the total energy of the system. Moreover, the calculation based on the temperature dependent heat capacity of many noninteracting enneadic clusters suggests that large interaction strengths are essential to sustain the highly symmetric ordered structure.