The free energy of the metastable supersaturated vapor via restricted ensemble simulations. III. An extension to the Corti and Debenedetti subcell constraint algorithm

Journal Article · Thu Apr 14 04:00:00 EDT 2016 · Journal of Chemical Physics

DOI:https://doi.org/10.1063/1.4945723· OSTI ID:22657918

Nie, Chu ^[1]; Geng, Jun ^[2]; Marlow, William H. ^[3]

---

1. School of Power and Mechanical Engineering, Wuhan University, Wuhan 430072 (China)
2. State Nuclear Power Research Institute (SNPRI), South Area, Future Science and Technology City, Changping District, Beijing 102209 (China)
3. Nuclear Engineering Department, Texas A&M University, 3133 TAMU, College Station, Texas 77843-3133 (United States)

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 N{sub m} allowed to appear inside a sphere of radius R, with this point as the center of the sphere. Both N{sub m} 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(N{sub m}, R) are found subject to different (N{sub m}, 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.

• OSTI ID: 22657918
• Journal Information: Journal of Chemical Physics, Journal Name: Journal of Chemical Physics Journal Issue: 14 Vol. 144; ISSN JCPSA6; ISSN 0021-9606
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
97 MATHEMATICS AND COMPUTING
ALGORITHMS
DENSITY
FORMATION FREE ENERGY
METASTABLE STATES
SIMULATION
VAPOR PRESSURE