Axial and angular correlations between colloidal particles in narrow cylindrical pores

Chávez-Páez, Martı́n; Medina‐Noyola, Magdaleno; Valdez-Covarrubias, M. A.

doi:10.1103/physreve.62.5179

Cited by 6 publications

(2 citation statements)

References 14 publications

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“…These approaches have made ample use of the standard techniques of the theory of simple liquids: integral equation methods, [1][2][3][4][5][6][7][8][9][10][11][12][13][14] density functional theory ͑DFT͒, [15][16][17][18][19][20][21] and computer simulations. 5,6,8,[10][11][12][22][23][24][25][26][27][28] Besides being applied to the description of the local concentration of a charged colloidal suspension in the vicinity of a flat infinite wall, these techniques have also been successfully employed in the study of the spatial arrangement of colloidal particles confined within closed geometries like planar slits, cylindrical pores, wedgelike regions, square ducts, etc. The distribution of a colloidal suspension near a flat, charged or neutral, wall can be considered as the limiting case of the distribution of colloids in the proximity of a very large, charged or neutral, spherical particle.…”

Section: Introductionmentioning

confidence: 99%

Correlations among colloidal particles confined to a spherical monolayer

Chávez-Páez¹,

González‐Mozuelos

Medina‐Noyola

et al. 2003

The Journal of Chemical Physics

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The internal structure of spherical colloidal monolayers of charged particles is studied here, both by means of Monte Carlo computer simulations and of an integral equation approach based on the application of the Ornstein-Zernike equation for spherical surfaces. The latter is complemented with a relatively fast and accurate numerical method for its solution, obtained by expanding the corresponding correlation functions in series of Legendre polynomials. It is found that the density correlations among the particles within the monolayer have some special features that differentiate them from the corresponding bulk corrections in open spaces. In particular, for a sufficiently small radius of the spherical monolayer, the distribution of particles around a particle fixed at one of the poles exhibits a peak at the opposite pole which is noticeably larger than the peaks immediately before it. It is also shown here that the introduction of a simple functional form with one adjustable parameter for the bridge function greatly enhances the fit between the theoretical approach and the simulation data.

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Section: Introductionmentioning

confidence: 99%

Correlations among colloidal particles confined to a spherical monolayer

Chávez-Páez¹,

González‐Mozuelos

Medina‐Noyola

et al. 2003

The Journal of Chemical Physics

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“…Interestingly, several theoretical studies have found that when small gaseous molecules are confined within these cavities they condense into a wide variety of molecular conformations such as linear arrays, zig-zag configurations, as well as helical and layered structures. [8][9][10] Actually, additional studies on similar related systems have demonstrated that the previous condensed phases and the associated structural transitions as a function of the number of stored molecules seems to be a more general feature of the cylindrical constraint since they have been also observed in colloidal suspensions confined in cylindrical pores, 11 when iodine atoms are encapsulated in SWNT's, 12 as well as for C 60 fullerenes trapped in the inside of carbon nanotubes of different radii. 4 The experimental results discussed in the previous paragraphs have stimulated many theoretical studies of gas adsorption in SWNT's arrays and additional relevant information concerning the role played by geometrical factors such as the nanotube's diameter and the intertube spacing in the sample has been mainly obtained through Monte Carlo simulations 13 and molecular dynamics techniques.…”

Section: Introductionmentioning

confidence: 95%

Energetics and Structural Properties of Nitrogen Molecules Confined in a Carbon Capsule

Barajas-Barraza¹,

Ramírez-Ruíz²,

Guirado-López³

2008

Jnl of Comp & Theo Nano

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The energetics and structural properties of N 2 molecules confined in a closed-ended (5,5) carbon capsule are investigated by means of semiempirical and density functional theory approaches. Similar to previous works addressing the encapsulation of molecular nitrogen in the endohedral cavities of carbon nanotubes we obtain, with increasing the number of encapsulated molecules, the formation of various non bonded molecular conformations namely, linear chains, zig-zag arrays, and several tubular helicoidal configurations. However, our density functional theory calculations reveal that the interaction potential between the encapsulated nitrogens and the internal surface of the carbon structure is not always repulsive for all our considered intermolecular distances. In fact, we have obtained the presence of a second energy minima in the N 2 -wall interaction energy curve, located near the inner surface, suggesting the possible existence of a more reactive carbon wall. For a single encapsulated nitrogen molecule, energy barriers of the order of 4 eV need to be overcome in order to achieve N 2 adsorption to the carbon structure. However, we have found that with the close proximity of neighboring co-adsorbed nitrogens (a fact that naturally occurs at high densities of stored N 2 ) these barriers are considerably lowered, favoring the existence of reaction paths through which adsorption to the internal surface could occur. Finally, by analyzing the electronic structure of our nitrogen containing carbon capsule we observe, with increasing the number of stored N 2 , the existence of sizable energy shifts and changes in the orbital nature of the highest-occupied and lowest-unoccupied molecular orbitals, which favours the possibility of having a sizable charge transfer and subsequent bond formation between the nitrogen species and the carbon wall. We believe that our results shed some new light into the properties of small molecules under extreme confinement and should be taken into account when analyzing the maximum storage capacity as well as the transport properties of nitrogen molecules encapsulated in carbon hollow nanostructures.

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