Accueil >
Production scientifique
(260) Production(s) de FIRLEJ L.
|
|
The role of local domain formation in the melting of hexane adlayers on graphite”, 
Auteur(s): Roth M.w., Firlej L., Kuchta B, Wexler C
Conference: APS March Meeting 2009 (Pittsburg, US, 2009-03-16)
Ref HAL: hal-00820291_v1
Exporter : BibTex | endNote
Résumé: Hexane is the shortest representative of the family of alkanes (linear models for polymers and proteins having formula CH3-(CH2)n-2-CH3 whose flexibility has any considerable impact on its dynamics. When adsorbed on graphite, a monolayer of hexane melts from a herringbone solid to a liquid at a temperature of approximately 175 K. To understand the mechanisms that drive this transition we have performed large scale molecular dynamics simulations (several runs over 100 ns, requiring a total of ~10 cpu-years of computation), using the most realistic model of the system (a fully atomistic representation of hexane, explicit site-by-site interaction with graphite carbons and CHARMM force field with carefully chosen adjustable parameters of interactions). We show that the melting of the low temperature herringbone solid phase starts with the formation of gauche defects at the ends of neighboring molecules, followed by molecular reorientation within a lamellae, without perturbing the overall structure of the adsorbed film. The melted phase has a domain-type structure with domains’ orientation that reflects the 6–fold symmetry of graphite. The size of domains decreases progressively when the temperature increases and the deformation of molecules to quasi globular shape is driven by progressive formation of gauche defects.
|
|
|
|
Test of the universality of the scaling energy in alkanes based on the melting transition of monolayers adsorbed on graphite
Auteur(s): Firlej L. , Kuchta B, Roth M.w., Wexler C
Conference: APS March Meeting 2009 (Pittsburg, US, 2009-03-16)
Ref HAL: hal-00820290_v1
Exporter : BibTex | endNote
Résumé: The quality of the results of computational treatment of complex systems depends crucially on the quality of the interaction potentials used. When modeling non-rigid molecules an essential difficulty resides in the correct accounting for all energies related to internal (conformational) degrees of freedom. Of particular importance is to avoid over- or under-counting of non-bonded intramolecular van der Waals and electrostatic interactions between close neighbors that are chemically bonded. In many force fields (e.g. CHARMM) 1-4 non-bonded interactions are scaled down by the use of the so-called scaling factor (SF). Typically, this scaling factor is assumed to be universal (and of the order of 0.5). In this talk, we study this universality hypothesis by comparing computational and experimental melting temperatures of alkane monolayers adsorbed on a solid graphite surface. Three alkanes (C6, C12, C24) of different lengths (7-30 Å) have been analyzed using an all-atom representation, standard CHARMM parameters, and various SF’s. We show that the scaling parameter has no universal value but it changes as a function of the molecular backbone length.
|
|
|
|
Quantum Energy Levels of Hydrogen Adsorbed on Nanoporous Carbons
Auteur(s): Olsen R.j, Firlej L., Kuchta B, Wexler C, Pfeifer P
Conference: International Workshop "Characterization of Porous Materials: from Angstroms to Millimeters (New Brunswick, US, 2009-06-24)
|
|
|
|
Quantum energy levels of hydrogen adsorbed on nanoporous carbons: an intrinsic probe for pore structure, and improving Monte Carlo simulations of adsorption
Auteur(s): Olsen R.j, Firlej L., Kuchta B, Wexler C, Pfeifer P
Conference: UM Energy Summit (Columbia, MO, US, 2009-04-22)
Ref HAL: hal-00820286_v1
Exporter : BibTex | endNote
Résumé: Quantum energy levels of hydrogen adsorbed on nanoporous carbons: an intrinsic probe for pore structure, and improving Monte Carlo simulations of adsorption
|
|
|
|
Structural and energetic factors in designing a perfect nano-porous sorbent for hydrogen storage
Auteur(s): Kuchta B, Firlej L., Olsen R.j, Wexler C, Pfeifer P
Conference: UM Energy Summit (Columbia, MO, US, 2009-04-22)
Ref HAL: hal-00820284_v1
Exporter : BibTex | endNote
Résumé: Structural and energetic factors in designing a perfect nano-porous sorbent for hydrogen storage
|
 |
Hydrogen storage for automobiles (gas adsorption in engineered carbon nanospaces)
Auteur(s): Wexler C, Roth M.w., Firlej L., Kuchta B, Pfeifer P
(Séminaires)
Department of Physics, University of Northern Iowa, Cedar Falls (Cedar Falls, US), 2009-02-18 |
|
Hydrogen adsorption in carbon nanopores for fuel cells applications
Auteur(s): Firlej L.
(Séminaires)
”, Institute of Molecular Physics, Polish Academy of Sciences (Poznan, PL), 2009-04-08 |
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 
