Toward a molecular theory of vapor-phase nucleation. V. Self-consistency in the decoupled dimer limit

Abstract

"Toward a molecular theory of vapor-phase nucleation. V. Self-consistency in the decoupled dimer limit" (1997). Xiao Cheng Zeng Publications. 69. http://digitalcommons.unl.edu/chemzeng/69Toward a molecular theory of vapor-phase nucleation. V. Self-consistency in the decoupled dimer limit The i/v cluster theory of vapor phase nucleation has been presented in a series of papers of which the present paper is No. V. The theory has experienced some evolution throughout this series. In the first paper an attempt was made to use the classical cluster of Lee, Barker, and Abraham ͑LBA cluster͒ that is so attractive for computer simulation. Among other things, that theory uses a so-called ''shell molecule'' that does not interact with the remaining molecules of the cluster. We show that this ''decoupling'' of the shell molecule leads to a result that is not internally consistent in the sense that dimers ͑which are really single vapor molecules͒ do not have the right concentration. We show how to repair this inconsistency so that the decoupling approximation can be used and, with it, the useful LBA cluster.

Computer simulation study of gas–liquid nucleation in a Lennard-Jones system

“…An expression very similar to the one above has been obtained by Reiss et al 27,[39][40][41][42][43] The only difference is that we make fewer assumptions; Reiss et al assumed that the surrounding gas is ideal and that there is no interaction between molecules that are inside the cluster and those outside. Instead, we have carried out the integration over the coordinates of the noncluster ͑solvent͒ particles, and the effect of the surrounding phase is adsorbed into the effective interactions between the particles that make up the cluster.…”

Binary nucleation of sulfuric acid-water: Monte Carlo simulation

“…95 The method is free of any arbitrariness involved in the definition of a cluster. Instead, it preferentially generates the physical clusters, defined as the density fluctuations that participate in nucleation, [35][36][37][38][39][40] and directly determines their equilibrium distribution without the computationally demanding free energy evaluation. In the present case of H 2 SO 4 /H 2 O binary system, however, Monte Carlo moves to create or annihilate an acid molecule will rarely be accepted since a hydrogen bond network will be seriously disturbed in the process.…”

“…One is a molecular level simulation, [33][34][35][36][37][38][39][40][41] which can be applied regardless of the complexity of the intermolecular interaction. However, the free energy of a cluster, the quantity of central importance in nucleation theory, is usually evaluated by integrating its internal energy obtained at different temperatures from separate simulations.…”

Direct evaluation of the equilibrium distribution of physical clusters by a grand canonical Monte Carlo simulation

“…We refer to this cluster as the LBA cluster. In an attempt to identify a physical cluster, Reiss et al [1][2][3][4][5][6] characterized the cluster by both i and v. The latter is related to the distance from the cluster's center of mass to the nearest ideal gas molecule, which serves as an index to organize the counting procedure in enumerating the configurational space of the entire vapor phase that is regarded as an ideal gas mixture of monomers and clusters of various sizes. As they have pointed out, [1][2][3][4][5] however, the identification of a physical cluster has to reflect the dynamics of the nucleation process.…”

“…The initial stage of this phase transition is the formation of a critical nucleus as a result of spontaneous density fluctuations in the metastable vapor phase. Since not all of the density fluctuations lead to nucleation, Reiss et al [1][2][3][4][5][6] posed a question regarding how to identify a physical cluster, which is defined as a density fluctuation that participates in the nucleation event. Moreover, if nucleation theory is to be formulated in terms of a cluster, as in the classical theory, 7 its precise characterization is the prerequisite of the theory.…”