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Title: Weak links between fast mobility and local structure in molecular and atomic liquids

We investigate by molecular-dynamics simulations, the fast mobility—the rattling amplitude of the particles temporarily trapped by the cage of the neighbors—in mildly supercooled states of dense molecular (linear trimers) and atomic (binary mixtures) liquids. The mixture particles interact by the Lennard-Jones potential. The non-bonded particles of the molecular system are coupled by the more general Mie potential with variable repulsive and attractive exponents in a range which is a characteristic of small n-alkanes and n-alcohols. Possible links between the fast mobility and the geometry of the cage (size and shape) are searched. The correlations on a per-particle basis are rather weak. Instead, if one groups either the particles in fast-mobility subsets or the cages in geometric subsets, the increase of the fast mobility with both the size and the asphericity of the cage is revealed. The observed correlations are weak and differ in states with equal relaxation time. Local forces between a tagged particle and the first-neighbour shell do not correlate with the fast mobility in the molecular liquid. It is concluded that the cage geometry alone is unable to provide a microscopic interpretation of the known, universal link between the fast mobility and the slow structural relaxation. We suggestmore » that the particle fast dynamics is affected by regions beyond the first neighbours, thus supporting the presence of collective, extended fast modes.« less
Authors:
 [1] ;  [2] ;  [1] ;  [3]
  1. Dipartimento di Fisica “Enrico Fermi,” Università di Pisa, Largo B. Pontecorvo 3, I-56127 Pisa (Italy)
  2. Laboratoire de Physique de l’École Normale Supérieure de Lyon, UMR CNRS 5672, 46 allée d’Italie, 69007 Lyon (France)
  3. (Italy)
Publication Date:
OSTI Identifier:
22415575
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Chemical Physics; Journal Volume: 142; Journal Issue: 12; Other Information: (c) 2015 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; ALCOHOLS; ALKANES; BINARY MIXTURES; COMPUTERIZED SIMULATION; CORRELATIONS; LENNARD-JONES POTENTIAL; LIQUIDS; MOBILITY; MOLECULAR DYNAMICS METHOD; PARTICLES; RELAXATION TIME; TRAPPING