title: The free energy of the metastable supersaturated vapor via restricted ensemble simulations. III. An extension to the Corti and Debenedetti subcell constraint algorithm.
abstract: In order to improve the sampling of restricted microstates in our previous work [C. Nie, J. Geng, and W. H. Marlow, J. Chem. Phys. 127, 154505 (2007); 128, 234310 (2008)] and quantitatively predict thermal properties of supersaturated vapors, an extension is made to the Corti and Debenedetti subcell constraint algorithm [D. S. Corti and P. Debenedetti, Chem. Eng. Sci. 49, 2717 (1994)], which restricts the maximum allowed local density at any point in a simulation box. The maximum allowed local density at a point in a simulation box is defined by the maximum number of particles Nm allowed to appear inside a sphere of radius R, with this point as the center of the sphere. Both Nm and R serve as extra thermodynamic variables for maintaining a certain degree of spatial homogeneity in a supersaturated system. In a restricted canonical ensemble, at a given temperature and an overall density, series of local minima on the Helmholtz free energy surface F(Nm, R) are found subject to different (Nm, R) pairs. The true equilibrium metastable state is identified through the analysis of the formation free energies of Stillinger clusters of various sizes obtained from these restricted states. The simulation results of a supersaturated Lennard-Jones vapor at reduced temperature 0.7 including the vapor pressure isotherm, formation free energies of critical nuclei, and chemical potential differences are presented and analyzed. In addition, with slight modifications, the current algorithm can be applied to computing thermal properties of superheated liquids.
authors.affiliation: School of Power and Mechanical Engineering, Wuhan University, Wuhan 430072, China.
authors.forename: Chu
authors.initials: C
authors.lastname: Nie
authors.affiliation: State Nuclear Power Research Institute (SNPRI), South Area, Future Science and Technology City, Changping District, Beijing 102209, People's Republic of China.
authors.forename: Jun
authors.initials: J
authors.lastname: Geng
authors.affiliation: Nuclear Engineering Department, Texas A&M University, 3133 TAMU, College Station, Texas 77843-3133, USA.
authors.forename: William H
authors.initials: WH
authors.lastname: Marlow