Contribution of physical clusters to phase behavior.
In a multicomponent fluid mixture, each physical cluster generated as an ensemble consisting of particles joined by each particle pair characterized by a bound state E(ij)+u(ij)</=0 can contribute towards prohibiting a transition from its macroscopically homogeneous phase to its macroscopically inhomogeneous phase. Here, E(ij) and u(ij) represent the relative kinetic energy and the pair potential for the pair of i and j particles, respectively. Branches constructing such physical clusters can confine unbound particles (i.e., particles constituting pairs characterized by an unbound state E(ij)+u(ij)>0) within regions surrounded by the branches, and can prohibit the boundaries of the regions from expanding freely. Particles belonging to one of the two groups characterizing constituents of a multicomponent fluid mixture (particles of A) should have a tendency to satisfy the condition E(ij)+u(ij)</=0; particles belonging to the other group (particles of B) should have a tendency to satisfy the condition E(ij)+u(ij)>0. The pair connectedness P(ij)(sigma) proportional to the probability that a particle of A is bound near another particle of A hardly varies as densities of particles of A increase, although the mean physical cluster size diverges to infinity as the densities approach values specified at the percolation threshold. Thus, each physical cluster should grow toward that having a larger span as densities of particles of A increase. According to this growth of physical clusters, the number of unbound particles confined by branches of the physical clusters is enhanced. The formation of physical clusters of particles of A can be considered as a primary phenomenon resulting in density fluctuations. Their formation results in the confinement of particles of B and A within regions surrounded by the branches of the physical clusters.
Kaneko
Tetsuo
T
Kurakenchikuzokeisha Company, Ltd., Shimo 1-27-22, Kita-ku, Tokyo 115-0042, Japan. kaneko@mailaps.org