Freezing transitions in a system of two-dimensional octupolar multipoles.

We have investigated the fluid-solid freezing transitions in a system of axially symmetric particles confined to a two-dimensional plane and interacting via purely repulsive octupolar interaction potential varying as the seventh power of the inverse interparticle separation. Both the one-component and two-component cases have been considered. The classical density functional theory of freezing has been employed to study the relative stability of the triangular solid phase of the system with respect to the fluid phase of the system using the structural inputs calculated by solving the Rogers-Young integral equation theory. Considering the freezing of the fluid into substitutionally disordered solid, in the case of binary mixtures, we observe that the temperature-composition phase diagram is a spindle for moderate particle asymmetries in the range 0.90-0.75. Further increasing the asymmetry to 0.70 results in the coexistence of the fluid phases of two different compositions.