Lennard-Jones fluid models applications

Yan, Q.L. de Pablo, J.J., Hyper-parallel tempering Monte Carlo Application to the Lennard-Jones fluid and the restricted primitive model, J. Chem. Phys. 1999, 111, 9509-9516... 

Carlo Application to the Lennard-Jones Fluid and the Restricted Primitive Model. 

Subsequent applications of semigrand methods have been numerous, as species-identity changes have become a standard practice when simulating mixtures. We would fail in an attempt to mention all such uses, so instead we will sample some of the more interesting applications and extensions. Hautman and Klein [22] examined, by molecular dynamics a breathing Lennard-Jones fluid of fluctuating particle diameter the breathing modes are introduced to better model molecules that are treated as LJ atoms. Liu... 

R. Radhakrishnan, K.E. Gubbins and M. Sliwinska-Bartkowiak, On the Existence of a Hexatic Phase in Confined Systems, Phys. Rev. Lett. 89 (2002) art. 076101 O l Q. Yan and J.J. de Pablo, Hyper-Parallel Tempering Monte Carlo Application to the Lennard-Jones Fluid and the Restricted Primitive Model, J. Chem. Phys. Ill (1999) pp. 9509-9516 W.A. Steele, Physical Interaction of Gases with Crystalline Solids 1. Gas-Solid Energies and Properties of Isolated Adsorbed Atoms, Surf. Sci 36 (1973) pp. 317-352... 

This section is devoted to studying the 2D Lennard-Jones model in order to serve as the basis in applying Steele s theory. In Section IVA the main studies about that model are summarized and commented on. In Section IVB, the most useful expressions for the equation of state of the model are given. In Section IVC we present results about the application of these equations, which are compared with other theoretical approaches to studying adsorption of 2D Lennard-Jones fluids onto perfectly flat surfaces. In Section FVD, the comparison with experimental results is made, including results for the adsorption isotherms, the spreading pressure, and the isosteric heat. Finally, in Section IVE we indicate briefly some details about the use of computer simulations to model the properties both of an isolated 2D Lennard-Jones system and of adsorbate-adsorbent systems. 

In mixed MD/MC simulations, some of the atoms are moved by the MD method and some of the atoms are moved by the MC method. LaBerge et al. [48] demonstrated that this method rigorously converges to the same equilibrium state as either MC or canonical MD alone. Thus, it was shown that the intermption of the forces produced by the application of the MC moves does not incorrectly bias the evolution of the MD particles. This technique was applied by the above authors to a Lennard-Jones fluid. It was anticipated that this model would be superior to either MD or MC on its own, in systems where some particles are more efficiently sampled by MD (for instance solvent motions), while others are more efficiently sampled by MC (for instance highly correlated motions). 

Application of DFT as a general methodology to classical systems was introduced by Ebner et al. (1976) in modeling the interfacial properties of a Lennard-Jones (LJ) fluid. The basis of all DFTs is that the Helmholtz free energy of an open system can be expressed as a unique functional of the density distribution of the constituent molecules. The equilibrium density distribution of the molecules is obtained by minimizing the appropriate free energy. 

The potential U(r ) is a sum over all intra- and intermolecular interactions in the fluid, and is assumed known. In most applications it is approximated as a sum of binary interactions, 17(r ) = IZ > w(rzj) where ry is the vector distance from particle i to particle j. Some generic models are often used. For atomic fluids the simplest of these is the hard sphere model, in which z/(r) = 0 for r > a and M(r) = c for r < a, where a is the hard sphere radius. A. more sophisticated model is the Lennard Jones potential... 

Application of the GDI method to the coexistence lines requires establishment of a coexistence datum on each. A point on the vapor-liquid line can be determined by a GE simulation. At high temperature the model behaves as a system of hard spheres, and the liquid-solid coexistence line approaches the fluid-solid transition for hard spheres, which is known [76,77]. Integration of liquid-solid coexistence from the hard-sphere transition proceeds much as described in Section III.C.l for the Lennard-Jones example. The limiting behavior (fi - 0) finds that /IP is well behaved and smoothly approaches the hard-sphere value [76,77] of 11.686 at f = 0 (unlike the LJ case, we need not work with j81/2). Thus the appropriate governing equation for the GDI procedure is... 

The use of nonlocal density functional theory (NLDFT) for modeling adsorption isotherms of Lennard-Jones (LJ) fluids in porous materials is now well-established [1-5], and is central to modem characterization of nanoporous carbons as well as a variety of other adsorbent materials [1-3]. The principal concept here is that in confined spaces the potential energy is related to the size of the pore [6], thereby permitting a pore size distribution (PSD) to be extracted by fitting adsorption isotherm data. For carbons the slit pore model is now well established, and known to be applicable to a variety of nanoporous carbon forms, where the underlying micro structure comprises a disordered aggregate of crystallites. Such slit width distributions are then useful in predicting the equilibrium [1-5] and transport behavior [7,8] of other fluids in the same carbon. 

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