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In statistical mechanics, the formation free energy of an i-mer can be understood as the Gibbs free energy change in a system consisting of pure monomers after and prior to the formation of the i-mer. For molecules interacting via Lennard-Jones potential, we have computed the formation free energy of a Stillinger i-mer [F. H. Stillinger, J. Chem. Phys. 38, 1486 (1963)] and a ten Wolde–Frenkel (tWF) [P. R. ten Wolde and D. Frenkel, J. Chem. Phys. 109, 9901 (1998)] i-mer at spinodal at reduced temperatures from 0.7 to 1.2. It turns out that the size of a critical Stillinger i-mer remains finite and its formation free energy is on the order of kBT, and the size of a critical tWF i-mer remains finite and its formation free energy is even higher. This can be explained by Binder's theory [K. Binder, Phys. Rev. A 29, 341 (1984)] that for a system, when approaching spinodal, if the Ginzburg criterion is not satisfied, a gradual transition will take place from nucleation to spinodal decomposition, where the free-energy barrier height is on the order of kBT. [ABSTRACT FROM AUTHOR]

The Helmholtz free energy of a constrained supersaturated vapor with a cluster size distribution consisting of clusters of various sizes is modeled as a mixture of hard spheres of various sizes attracting each other. This model naturally takes into account monomer-monomer and monomer-cluster interactions, so it implicitly pertains to nonideal gases, unlike prior work. Based on this model, the expressions for the equilibrium concentration and the formation free energies of clusters in a metastable supersaturated vapor have been derived. These results indicate that the widely used formula, ni = n1exp(−βΔGi), that computes the formation free energy of a cluster does not work at high supersaturations. As an example, the formation free energies of clusters with Stillinger's physical cluster definition in metastable, highly supersaturated vapors interacting via Lennard-Jones potential are studied using these expressions. Noticeable differences have been found for both the formation free energies of clusters and sizes of the critical clusters computed from our proposed expressions vs those from the formula ni = n1exp(−βΔGi). [ABSTRACT FROM AUTHOR]

Extensive restricted canonical ensemble Monte Carlo simulations [D. S. Corti and P. Debenedetti, Chem. Eng. Sci. 49, 2717 (1994)] were performed. Pressure, excess chemical potential, and excess free energy with respect to ideal gas data were obtained at different densities of the supersaturated Lennard-Jones (LJ) vapor at reduced temperatures from 0.7 to 1.0. Among different constraints imposed on the system studied, the one with the local minimum of the excess free energy was taken to be the approximated equilibrium state of the metastable LJ vapor. Also, a comparison of our results with molecular dynamic simulations [A. Linhart et al., J. Chem. Phys. 122, 144506 (2005)] was made. [ABSTRACT FROM AUTHOR]

A new electrically addressed and thermally erased cholesteric cell has been investigated. The helical pitch of the cholesteric mixture becomes longer with increasing temperature. After an electric field is applied to the mixture, a focal conic texture is formed. When being heated, the cholesteric phase has a tendency to adopt a planar texture. This is because the planar texture is stabler than the focal conic one when the pitch is longer. Both textures are stable at room temperature without external fields. [ABSTRACT FROM AUTHOR]