Article
Simulation of phase boundaries using constrained cell models.
Department of Chemical and Biomolecular Engineering, University of California, Los Angeles, CA 90095, USA.
Journal of Physics Condensed Matter
(Impact Factor: 2.22).
08/2012;
24(37):375105.
DOI: 10.1088/09538984/24/37/375105
Source: PubMed

Article: Communication: Direct determination of triplepoint coexistence through cell model simulation.
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ABSTRACT: In simulations of fluidsolid coexistence, the solid phase is modeled as a constrained system of WignerSeitz cells with one particle per cell. This model, commonly referred to as the constrained cell model, is a limiting case of a more general cell model, which is formed by considering a homogeneous external field that controls the number of particles per cell and, hence, the relative stability of the solid against the fluid phase. The generalized cell model provides a link that connects the disordered, fluid phase with the ordered, solid phase. In the present work, the phase diagram of this model is investigated through multicanonical simulations at constant pressure and histogram reweighting techniques for a system of 256 LennardJones particles. The simulation data are used to obtain an estimate of the triple point of the LennardJones system. The triplepoint pressure is found to be higher compared to previous work. The likely explanation for this discrepancy is the highly compressible nature of the gas phase.The Journal of Chemical Physics 10/2012; 137(14):141101. DOI:10.1063/1.4758698 · 3.12 Impact Factor 
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ABSTRACT: In the present work, a simulation method based on cell models is used to deduce the fluid–solid transition of a system of particles that interact via a pair potential, $\phi \left( r\right) $ ϕ ( r ) , which is of the form $\phi \left( r\right) = 4\epsilon \left[ \left( \sigma /r\right) ^{2n} \left( \sigma /r\right) ^{n}\right] $ ϕ ( r ) = 4 ϵ [ ( σ / r ) 2 n − ( σ / r ) n ] with $n=10$ n = 10 . The simulations are implemented under constantpressure conditions on a generalized version of the constrained cell model. The constrained cell model is constructed by dividing the volume into Wigner–Seitz cells and confining each particle in a single cell. This model is a special case of a more general cell model which is formed by introducing an additional field variable that controls the number of particles per cell and, thus, the relative stability of the solid against the fluid phase. High field values force configurations with one particle per cell and thus favor the solid phase. Fluid–solid coexistence on the isotherm that corresponds to a reduced temperature of 2 is determined from constantpressure simulations of the generalized cell model using tempering and histogram reweighting techniques. The entire fluid–solid phase boundary is determined through a thermodynamic integration technique based on histogram reweighting, using the previous coexistence point as a reference point. The vapor–liquid phase diagram is obtained from constantpressure simulations of the unconstrained system using tempering and histogram reweighting. The phase diagram of the system is found to contain a stable critical point and a triple point. The phase diagram of the corresponding constrained cell model is also found to contain both a stable critical point and a triple point.International Journal of Thermophysics 04/2013; 35(910). DOI:10.1007/s1076501314302 · 0.62 Impact Factor
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