Comparisons Between Integral Equation Theory and Molecular Dynamics Simulations for Atomistic Models of Polyethylene Liquids

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Molecular dynamics (MD) simulations were performed on dense liquids of polyethylene chains of 24 and 66 united atom CH{sub 2} units. A series of models was studied ranging in atomistic detail from coarse-grained, freely-jointed, tangent site chains to realistic, overlapping site models subjected to bond angle restrictions and torsional potentials. These same models were also treated with the self-consistent, polymer reference interaction site model (PRISM) theory. The intramolecular and total structure factors, as well as, the intermolecular radial distribution functions g(r) and direct correlation functions C(r) were obtained from theory and simulation. Angular correlation functions were also simulation obtained from ... continued below

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41 p.

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Curro, John G.; Webb III, Edmund B.; Grest, Gary S.; Weinhold, Jeffrey D.; Putz, Mathias & McCoy, John D. July 21, 1999.

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  • Sandia National Laboratories
    Publisher Info: Sandia National Labs., Albuquerque, NM, and Livermore, CA (United States)
    Place of Publication: Albuquerque, New Mexico

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Molecular dynamics (MD) simulations were performed on dense liquids of polyethylene chains of 24 and 66 united atom CH{sub 2} units. A series of models was studied ranging in atomistic detail from coarse-grained, freely-jointed, tangent site chains to realistic, overlapping site models subjected to bond angle restrictions and torsional potentials. These same models were also treated with the self-consistent, polymer reference interaction site model (PRISM) theory. The intramolecular and total structure factors, as well as, the intermolecular radial distribution functions g(r) and direct correlation functions C(r) were obtained from theory and simulation. Angular correlation functions were also simulation obtained from the MD simulations. Comparisons between theory and reveal that PRISM theory works well for computing the intermolecular structure of coarse-grained chain models, but systematically underpredicts the extent of intermolecular packing as more atomistic details are introduced into the model. A consequence of g(r) having insufficient structure is that the theory yields an isothermal compressibility that progressively becomes larger, relative to the simulations, as overlapping the PRISM sites and angular restrictions are introduced into the model. We found that theory could be considerably improved by adding a tail function to C(r) beyond the effective hard core diameter. The range of this tail function was determined by requiring the theory to yield the correct compressibility.

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41 p.

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OSTI as DE00009479

Medium: P; Size: 41 pages

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  • Journal Name: Journal of Chemical Physics; Other Information: Submitted to Journal of Chemical Physics

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  • Report No.: SAND99-1918J
  • Grant Number: AC04-94AL85000
  • DOI: 10.1063/1.480335 | External Link
  • Office of Scientific & Technical Information Report Number: 9479
  • Archival Resource Key: ark:/67531/metadc794669

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  • July 21, 1999

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  • Dec. 19, 2015, 7:14 p.m.

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  • April 12, 2017, 3:07 p.m.

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Curro, John G.; Webb III, Edmund B.; Grest, Gary S.; Weinhold, Jeffrey D.; Putz, Mathias & McCoy, John D. Comparisons Between Integral Equation Theory and Molecular Dynamics Simulations for Atomistic Models of Polyethylene Liquids, article, July 21, 1999; Albuquerque, New Mexico. (digital.library.unt.edu/ark:/67531/metadc794669/: accessed September 24, 2018), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.