5 research outputs found
Mesoscopic theory for inhomogeneous mixtures
Mesoscopic density functional theory for inhomogeneous mixtures of sperical
particles is developed in terms of mesoscopic volume fractions by a systematic
coarse-graining procedure starting form microscopic theory. Approximate
expressions for the correlation functions and for the grand potential are
obtained for weak ordering on mesoscopic length scales. Stability analysis of
the disordered phase is performed in mean-field approximation (MF) and beyond.
MF shows existence of either a spinodal or a -surface on the
volume-fractions - temperature phase diagram. Separation into homogeneous
phases or formation of inhomogeneous distribution of particles occurs on the
low-temperature side of the former or the latter surface respectively,
depending on both the interaction potentials and the size ratios between
particles of different species. Beyond MF the spinodal surface is shifted, and
the instability at the -surface is suppressed by fluctuations. We
interpret the -surface as a borderline between homogeneous and
inhomogeneous (containing clusters or other aggregates) structure of the
disordered phase. For two-component systems explicit expressions for the MF
spinodal and -surfaces are derived. Examples of interaction potentials
of simple form are analyzed in some detail, in order to identify conditions
leading to inhomogeneous structures.Comment: 6 figure
Non-Perturbative Renormalization Group for Simple Fluids
We present a new non perturbative renormalization group for classical simple
fluids. The theory is built in the Grand Canonical ensemble and in the
framework of two equivalent scalar field theories as well. The exact mapping
between the three renormalization flows is established rigorously. In the Grand
Canonical ensemble the theory may be seen as an extension of the Hierarchical
Reference Theory (L. Reatto and A. Parola, \textit{Adv. Phys.}, \textbf{44},
211 (1995)) but however does not suffer from its shortcomings at subcritical
temperatures. In the framework of a new canonical field theory of liquid state
developed in that aim our construction identifies with the effective average
action approach developed recently (J. Berges, N. Tetradis, and C. Wetterich,
\textit{Phys. Rep.}, \textbf{363} (2002))