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Title: Comparison of several classical density functional theories for the adsorption of flexible chain molecules into cylindrical nanopores

Adsorption of flexible oligomers into narrow cylindrical pores has been studied by means of several versions of classical density functional theory (CDFT) and Monte Carlo simulation. The adsorption process is interesting to study due to the competition between the entropic depletion of oligomers from the pores and the wall–oligomer attraction. It is also challenging to describe using current CDFTs, which tend to overestimate the amount of the adsorbed fluid. From a comparison of several different CDFT approaches, we find that this is due to the assumption of ideal or freely jointed chain conformations. Moreover, it is demonstrated that it is impossible to obtain a reasonable description of the adsorption isotherms without taking into account accurate contact values in the distribution functions describing the structure of the reference monomer fluid. At low densities, more accurate result are obtained in comparison with Monte Carlo simulation data when accurate contact values are incorporated into the theory rather than the more commonly used hard-sphere contact value. However, even the CDFT with accurate contact values still overestimates the amount of the adsorbed fluid due to the ideal or freely jointed chain approximation, used for the description of chain conformations in most CDFT approaches. We findmore » that significant improvement can achieved by employing self-consistent field theory, which samples self-avoiding chain conformations and decreases the number of possible chain conformations, and, consequently, the amount of the adsorbed fluid.« less
Authors:
 [1] ;  [2] ;  [1] ;  [3] ;  [1] ;  [3]
  1. Department of Chemical and Biomolecular Engineering, Vanderbilt University, Nashville, Tennessee 37235 (United States)
  2. (Ukraine)
  3. (United States)
Publication Date:
OSTI Identifier:
22253740
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Chemical Physics; Journal Volume: 139; Journal Issue: 23; Other Information: (c) 2013 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY; ADSORPTION; ADSORPTION ISOTHERMS; COMPUTERIZED SIMULATION; DENSITY; DENSITY FUNCTIONAL METHOD; DISTRIBUTION FUNCTIONS; FLUIDS; MONTE CARLO METHOD; SELF-CONSISTENT FIELD