Studies of porosity and diffusion coefficient in porous matrices by computer simulations

Domínguez, Héctor; Rivera, Margarita

doi:10.1080/00268970210164437

Cited by 11 publications

(5 citation statements)

References 32 publications

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“…It is worth noting that alternatively (cf., for example, the molecular dynamics simulation studies [35][36][37] ), the self-diffusion coefficient can be calculated from the equation for the mean square of the particle displacement:…”

Section: The Brownian Dynamics Simulationmentioning

confidence: 99%

“…[28][29][30] There are several important studies in which the study of ionic self-diffusion was extended to media with randomly distributed charges. [31][32][33][34][35][36][37] Among theoretical papers we need to mention the works of Chandler, Chakraborty and coworkers 31,32 who studied the classical diffusion of particles in random media. Monte Carlo simulations of diffusion of ionic particles in charged, disordered media were presented by Mehrabi and Sahimi 33 and commented by Deem.…”

Section: Introductionmentioning

confidence: 99%

“…Monte Carlo simulations of diffusion of ionic particles in charged, disordered media were presented by Mehrabi and Sahimi 33 and commented by Deem. 34 Finally, Dominguez and coworkers [35][36][37] published a series of molecular dynamics simulations to study the diffusion of charged fluids in charged porous matrices. The diffusion of hard-sphere fluids in disordered media composed of quenched hard spheres, which is an important limiting case, was treated by Chang and coworkers.…”

Section: Introductionmentioning

confidence: 99%

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Self-diffusion coefficients of ions in the presence of charged obstacles

Jardat

Hribar-Lee

Vlachy

2008

Phys. Chem. Chem. Phys.

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The self-diffusion coefficient of ions of the charge- and size-symmetric +1:-1 (or +2:-2) electrolyte was studied in the presence of ionic obstacles (matrix) representing disordered media. For this purpose the Brownian dynamics method was used, complemented with the replica Ornstein-Zernike theory for the partly-quenched systems. The matrix was prepared by a rapid quench of the size-symmetric +1:-1 (in few cases also of +2:-2) electrolyte solution being in equilibrium at (temperature, relative permittivity) T0, epsilon. Within the matrix the charge- and size-symmetric (+1:-1 or +2:-2) electrolyte at T1, epsilon1 was distributed. This component was fully mobile (annealed) and in thermodynamic equilibrium with the matrix. In this study a special attention was paid to the self-diffusion of the annealed ions. The ratio D/D degrees, where D degrees is the self-diffusion coefficient of ions at infinite dilution, has been studied for various model parameters varying the concentration of all species in the system. The presence of charged obstacles decreases the self-diffusion of the annealed electrolyte; the D/D degrees values are lower in the partly-quenched mixtures than in the fully annealed electrolyte of the same concentration. In the investigated range of concentrations and solvent dielectric constants, the D/D degrees values first increased with the increased concentration of annealed electrolyte present and then decreased. An increase of the strength of the Coulomb interaction between annealed ions, or between annealed and quenched charges, yielded a decrease of the self-diffusion. In the range of concentrations investigated in this work, the decrease is mainly due to the Coulomb interaction with the matrix, since the presence of neutral obstacles did not modify the diffusion properties with respect to the situation without obstacles.

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Section: The Brownian Dynamics Simulationmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Self-diffusion coefficients of ions in the presence of charged obstacles

Jardat

Hribar-Lee

Vlachy

2008

Phys. Chem. Chem. Phys.

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“…In addition to improved size selectivity in molecular sieving, the main benefit of templating is the reduction of weight of the material with only a modest decrease in strength [17]. The effect of templating on diffusivity has been studied using molecular dynamics simulations [18] where it was observed that for a given porosity, non-activated diffusivity of a fluid within a material prepared without a template is higher than in any other templated material. That is, while the overall porosity of the templated material is higher, the lower effective porosity of the walls surrounding the templated pores leads to an overall reduction in the diffusivity.…”

Section: Introductionmentioning

confidence: 98%

Diffusion enhancement in composites of nanotubes and porous structures

Srebnik

Sheintuch

2009

Molecular Simulation

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Composites are often used to obtain enhanced material properties, including improved mechanical performance, enhanced conductivity, increased transport and other properties. Recent advances in carbon nanotube (CNT) composite porous materials suggest that CNTs may offer a greater advantage than conventional fillers, not only due to their extraordinary mechanical and electronic properties but also due to their smooth potential surface that allows for relatively high flux through the tubes. Using lattice Monte Carlo simulation, we study activated diffusion through various porous structures, and compare it with CNT composite materials. Flux enhancement is found to be substantial beyond the percolation threshold of nanotube aggregates, especially for relatively low-porosity structures. The simulation results are captured by a simple model that accounts for two contributions to the flux: diffusion within the percolating nanotube clusters and inside the porous substrate. Such porous structures may form better catalysts, membranes or molecular sieves where an increase in both surface area and flux is required.

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“…Monte Carlo simulations of diffusion of ionic particles in charged, disordered media were presented by Mehrabi and Sahimi 53 and commented by Deem. 54 Finally, Dominguez and Rivera 55,56 published a series of molecular dynamics simulation studies of the diffusion of charged fluids in charged porous matrices. The diffusive relaxation of a colloidal fluid adsorbed in a porous medium was studied by Medina-Noyola and coworkers.…”

Section: Introductionmentioning

confidence: 99%

Partly-quenched systems containing charges. Structure and dynamics of ions in nanoporous materials

Hribar-Lee

Lukšič

Vlachy

2011

Annu. Rep. Prog. Chem., Sect. C: Phys. Chem.

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Disordered porous materials filled with liquid or solution may be considered as partly-quenched, i.e., as systems in which some of the degrees of freedom are quenched and others annealed. In such cases, the statistical-mechanical averages used to calculate the system's thermodynamical properties become double ensemble averages: first over the annealed degrees of freedom and then over all possible values of the quenched variables. In this respect, the quenched-annealed systems differ from regular mixtures. The multi-faceted applications of the partly-quenched systems to a kaleidoscope of technological and biological processes make the understanding of these systems important and of interest. Present contribution reviews recent developments in theory and simulation of partly-quenched systems containing charges. Specifically, two different models of such systems are discussed: (a) the model in which the nanoporous system (matrix subsystem) formed by charged obstacles is electroneutral, and (b) the model, where the subsystem of obstacles has some net charge. The latter model resembles, for example, the situation in ion exchange resins etc. Various theoretical methods are applied to investigate structural and dynamical peculiarities of such systems. One is the replica Ornstein-Zernike theory, especially adapted for charged systems, and the other is the Monte Carlo computer simulation method. These two approaches are well suited to study thermodynamical parameters, such as the mean activity coefficient of the annealed electrolyte or Donnan's exclusion parameter. Highly relevant issue of dynamics of ions in partly-quenched systems is also addressed. For this purpose, the Brownian dynamic method is used: the self-diffusion coefficients of ions are calculated for various model parameters and discussed in light of the experimental data. These results, together with the thermodynamical data mentioned above, provide additional evidence that properties of the adsorbed fluid substantially differ from those of its bulk counterpart.

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Studies of porosity and diffusion coefficient in porous matrices by computer simulations

Cited by 11 publications

References 32 publications

Self-diffusion coefficients of ions in the presence of charged obstacles

Self-diffusion coefficients of ions in the presence of charged obstacles

Diffusion enhancement in composites of nanotubes and porous structures

Partly-quenched systems containing charges. Structure and dynamics of ions in nanoporous materials

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