title: Structural disorder and anomalous diffusion in random packing of spheres.
abstract: Nowadays Nuclear Magnetic Resonance diffusion (dNMR) measurements of water molecules in heterogeneous systems have broad applications in material science, biophysics and medicine. Up to now, microstructural rearrangement in media has been experimentally investigated by studying the diffusion coefficient (D(t)) behavior in the tortuosity limit. However, this method is not able to describe structural disorder and transitions in complex systems. Here we show that, according to the continuous time random walk framework, the dNMR measurable parameter α, quantifying the anomalous regime of D(t), provides a quantitative characterization of structural disorder and structural transition in heterogeneous systems. To demonstrate this, we compare α measurements obtained in random packed monodisperse micro-spheres with Molecular Dynamics simulations of disordered porous media and 3D Monte Carlo simulation of particles diffusion in these kind of systems. Experimental results agree well with simulations that correlate the most used parameters and functions characterizing the disorder in porous media.
authors.affiliation: 1] Physics Department, Sapienza University of Rome, P. le A. Moro, 5 00185 Rome, Italy [2] CNR IPCF UOS Roma, Physics Department, Sapienza University of Rome, P. le A. Moro, 5 00185 Rome, Italy.
authors.forename: M
authors.initials: M
authors.lastname: Palombo
authors.forename: A
authors.initials: A
authors.lastname: Gabrielli
authors.forename: V D P
authors.initials: VD
authors.lastname: Servedio
authors.forename: G
authors.initials: G
authors.lastname: Ruocco
authors.forename: S
authors.initials: S
authors.lastname: Capuani
references.citation: Phys Rev E Stat Phys Plasmas Fluids Relat Interdiscip Topics. 1999 Oct;60(4 Pt B):4551-8
references.pmid: 11970312
references.citation: Biophys J. 1994 Feb;66(2 Pt 1):394-401
references.pmid: 8161693
references.citation: J Chem Phys. 2011 Jul 21;135(3):034504
references.pmid: 21787010
references.citation: Phys Rev Lett. 2000 Mar 6;84(10):2064-7
references.pmid: 11017210
references.citation: Phys Rev E Stat Nonlin Soft Matter Phys. 2005 Jun;71(6 Pt 1):061302
references.pmid: 16089730
references.citation: J Magn Reson B. 1996 Jun;111(3):209-19
references.pmid: 8661285
references.citation: Biophys J. 2007 Feb 15;92(4):1178-91
references.pmid: 17142285
references.citation: Nat Phys. 2011 Jun 1;7(6):508-514
references.pmid: 21686083
references.citation: Magn Reson Med. 1999 Sep;42(3):526-40
references.pmid: 10467297
references.citation: Phys Rev E Stat Nonlin Soft Matter Phys. 2001 Aug;64(2 Pt 1):021605
references.pmid: 11497601
references.citation: Phys Rev E Stat Nonlin Soft Matter Phys. 2005 Mar;71(3  Pt 1):030301
references.pmid: 15903397
references.citation: Phys Rev E Stat Nonlin Soft Matter Phys. 2005 Jan;71(1 Pt 1):011105
references.pmid: 15697578
references.citation: Phys Rev E Stat Nonlin Soft Matter Phys. 2010 Dec;82(6 Pt 1):061302
references.pmid: 21230667
references.citation: Biophys J. 2004 Nov;87(5):3518-24
references.pmid: 15339818
references.citation: Nat Mater. 2004 Sep;3(9):645-50
references.pmid: 15300243
references.citation: Phys Rev E Stat Phys Plasmas Fluids Relat Interdiscip Topics. 2000 Jul;62(1 Pt B):993-1001
references.pmid: 11088556
references.citation: Phys Rev E Stat Nonlin Soft Matter Phys. 2010 Nov;82(5 Pt 1):050301
references.pmid: 21230422
references.citation: Phys Rev E Stat Nonlin Soft Matter Phys. 2004 Dec;70(6 Pt 2):066131
references.pmid: 15697458
references.citation: Phys Rev E Stat Nonlin Soft Matter Phys. 2004 Oct;70(4 Pt 1):041108
references.pmid: 15600398