Condensed Matter Physics, 2012, vol. 15, No. 2, p. 23604:1-16
DOI:10.5488/CMP.15.23604           arXiv:1201.0464

Title: Effect of mesoscopic fluctuations on equation of state in cluster-forming systems
  A. Ciach (Institute of Physical Chemistry, Polish Academy of Sciences, 01-224 Warszawa, Poland) ,
  O. Patsahan (Institute for Condensed Matter Physics of the National Academy of Sciences of Ukraine, 1 Svientsitskii Str., 79011 Lviv, Ukraine)

Equation of state for systems with particles self-assembling into aggregates is derived within a mesoscopic theory combining density functional and field-theoretic approaches. We focus on the effect of mesoscopic fluctuations in the disordered phase. The pressure - volume fraction isotherms are calculated explicitly for two forms of the short-range attraction long-range repulsion potential. Mesoscopic fluctuations lead to an increased pressure in each case, except for very small volume fractions. When large clusters are formed, the mechanical instability of the system is present at much higher temperature than found in mean-field approximation. In this case phase separation competes with the formation of periodic phases (colloidal crystals). In the case of small clusters, no mechanical instability associated with separation into dilute and dense phases appears.

Key words: clusters, self-assembly, equation of state, mesoscopic fluctuations
PACS: 61.20.Gy, 64.10.+h, 64.60.De, 64.75.Yz

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