Dislocation-mediated melting near isostructural critical points

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Abstract
We study the interplay between an isostructural critical point and dislocation-mediated two-dimensional melting, using a combination of Landau and continuum elasticity theory. If dislocations are excluded, coupling to the elastic degrees of freedom leads to mean-field critical exponents. When dislocations are allowed, modified elastic constants lead to a phase buried in the solid state near the critical point. Consistent with a proposal of Bladon and Frenkel, we find an intervening hexatic phase near the critical point of the first-order isostructural transition line. Very close to the critical point, a transition from the hexatic phase to a modulated-bond-angle state is possible. Ising transitions in symmetrically confined two-dimensional colloidal crystals with attractive wall potentials require a different model free energy, which we also discuss. © 1996 The American Physical Society.
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