The structure and phase behavior of a two-dimensional system with purely repulsive core-softened and long-range interactions are studied using Monte Carlo computer simulations. The pair interactions are of the form, $u\left(r\right)=4\mathrm{}\epsilon \left[\right(\sigma {/r)}^{12}-\left(\sigma {/r)}^6\right]+{\epsilon }^{\prime }(\sigma {/r)}^3,$ with the energy parameter, ${\epsilon }^{\prime }=(8\mathrm{}\sqrt{6}/9)\epsilon$ chosen to give a stationary point of inflection in the pair potential at ${r=6\mathrm{}}^{1/6}\sigma .$ This potential approximates the effective interparticle interactions for a two-dimensional dipolar system in a strong field aligned perpendicular to the plane. The low-temperature portion of the phase diagram is sketched out, and the static properties of the various phases are analyzed in some detail. At low temperatures a variety of interesting states are in evidence, including: fluids with chainlike, striped, and 6–10 sided polygon structural motifs; low-density and high-density triangular crystalline phases; and defective Kagomé lattices. It is shown that clustering is driven by the presence of the repulsive shoulder in the pair potential. Other features, such as the presence of a disordered phase with a network structure, are due to the long-range ${(1/r}^3)$ repulsive tail in the potential. The relevance of the simulation results to experimental work, including materials synthesis, is briefly discussed.

• Received 4 August 2003

DOI:https://doi.org/10.1103/PhysRevE.68.061506