Grand Canonical Monte Carlo simulation

Grand Canonical Monte Carlo Simulations of Adsorption Processe ... 

One application of the grand canonical Monte Carlo simulation method is in the study ol adsorption and transport of fluids through porous solids. Mixtures of gases or liquids ca separated by the selective adsorption of one component in an appropriate porous mate The efficacy of the separation depends to a large extent upon the ability of the materit adsorb one component in the mixture much more strongly than the other component, separation may be performed over a range of temperatures and so it is useful to be to predict the adsorption isotherms of the mixtures. 

A7 Ethane/methane selectivity calculated from grand canonical Monte Carlo simulations of mixtures in slit IS at a temperature of 296 K. The selectivity is defined as the ratio of the mole fractions in the pore to the ratio of mole fractions in the bulk. H is the slit width defined in terms of the methane collision diameter (Tch,- (Figure awn from Crackncll R F, D Nicholson and N Quirke 1994. A Grand Canonical Monte Carlo Study ofLennard-s Mixtures in Slit Pores 2 Mixtures of Two-Centre Ethane with Methane. Molecular Simulation 13 161-175.)... 

To conclude, the introduction of species-selective membranes into the simulation box results in the osmotic equilibrium between a part of the system containing the products of association and a part in which only a one-component Lennard-Jones fluid is present. The density of the fluid in the nonreactive part of the system is lower than in the reactive part, at osmotic equilibrium. This makes the calculations of the chemical potential efficient. The quahty of the results is similar to those from the grand canonical Monte Carlo simulation. The method is neither restricted to dimerization nor to spherically symmetric associative interactions. Even in the presence of higher-order complexes in large amounts, the proposed approach remains successful. 

The discussion in Refs. 17 and 18 is illustrative. Torrie [17] presented very important results for grand canonical Monte Carlo simulations of an electrical double layer in 2 1 electrolytes. Those results provide very convincing evidence that C < 0 can occur under cr-control. However, instead of analyzing the consequences of this fact for real systems, the author simply quotes the statement [21] that sign of C is not restricted, even for -control. Reliance on this result (see a critique in Ref. 22) simply ignored the problem and discouraged closer study of this system. 

Woo, H. J. Dinner, A. R. Roux, B., Grand canonical Monte Carlo simulations of water in protein environments, J. Chem. Phys. 2004,121, 6392-6400. 

P. Kowalczyk, H. Tanaka, R. Holyst, K. Kaneko, T. Ohmori, and J. Miyamoto, Storage of hydrogen at 303 K in graphite slitlike pores from grand canonical Monte Carlo simulation, J. Phys. Chem. B, 109, 17174-17183 (2005). 

Abstract We use Nuclear Magnetic Resonance relaxometry (i.e. the frequency variation of the NMR relaxation rates) of quadrupolar nucleus ( Na) and H Pulsed Gradient Spin Echo NMR to determine the mobility of the counterions and the water molecules within aqueous dispersions of clays. The local ordering of isotropic dilute clay dispersions is investigated by NMR relaxometry. In contrast, the NMR spectra of the quadrupolar nucleus and the anisotropy of the water self-diffusion tensor clearly exhibit the occurrence of nematic ordering in dense aqueous dispersions. Multi-scale numerical models exploiting molecular orbital quantum calculations, Grand Canonical Monte Carlo simulations, Molecular and Brownian Dynamics are used to interpret the measured water mobility and the ionic quadrupolar relaxation measurements. 

Vitalis, A., Baker, N. A., and McCammon, J. A. (2004). ISIM A program for grand canonical Monte Carlo simulations of the ionic environment of biomolecules. Mol. Simul. 30, 45—61. 

Kowalczyk P, Tanaka H, Kaneko K, Terzyk AP, and Do DD. Grand canonical Monte Carlo simulation study of methane adsorption at an open graphite surface and in slit like carbon pores at 273 K. Langmuir, 2005 21(12) 5639-5646. 

Challa S.R., Sholl D.S., Johnson J.K., Adsorption and separation of hydrogen isotopes in carbon nanotubes Multicomponent grand canonical Monte Carlo simulations, J.Chem.Physics, 2002,116(2) 814-824. 

The complexity of xylene adsorption over zeolites is too high to predict the selectivity from the chemical properties of the zeolite only (electronegativity of the cations, charge of the framework oxygens). The interactions between xylenes and the zeolite must necessarily be considered, which explains the important development of molecular simulation methods. This is supported by the work of V. Lachet et al. (18) who succeeded in reproducing the inversion of selectivity between KY and NaY with Grand Canonical Monte Carlo Simulations. 

A Grand Canonical Monte Carlo simulation study... 

Figure 3 Isotherms with grand canonical Monte Carlo simulations in periodic boundeiry conditions, y = 0.9 and T = 0.5.

A grand canonical Monte Carlo simulation study of water adsorption in a Vycor-like disordered mesoporous material at 300 K. 

Grand Canonical Monte Carlo simulation is used to investigate the properties of water (fluid of most importance) confined in mesoporous Controled Porous Glass (Vycor-like) numerically obtained by the off-lattice method developed by P. Levitz [Adv. Coll. Int. Sci. 76-77 (1998), 71]. We first outline the interaction model and give the adsorption isotherm obtained at 300 K. Good agreement is found with available experimental results. 

Adsorption isotherms and heats of adsorption were calculated using Grand Canonical Monte Carlo simulations. Details of the simulation are described in a previous publication [11]. Surface excess amount adsorbed was calculated by subtracting the bulk density from the pore density at the conditions of the simulation. The pore volume is necessary to calculate the pore density. In this work, the helium pore volume using ane= 0.264nm was determined by MC integration, similar to the procedure used for the PSD. 

In the molecular simulation of adsorption in confined space such as pores of adsorbent, the most widely used and success l ensemble is the grand canonical Monte Carlo simulation. In this ensemble, we specify the chemical potential of the fluid,p, that the candidate pore is immersed in, the size of the pore, and the temperature. 

Adsorption of binary gas mixtures in the presence of ad-ad interactions is studied through grand canonical Monte Carlo simulation in the framework of the lattice-gas model. The disordered surface has been characterized by patches of shallow and deep sites, arranged in a chessboard-like topography. 

HYSTERESIS IN GRAND CANONICAL MONTE CARLO SIMULATIONS... 

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