Free volume cannot explain the spatial heterogeneity of Debye–Waller factors in a glass-forming binary alloy

Widmer‐Cooper, Asaph; Harrowell, Peter

doi:10.1016/j.jnoncrysol.2006.01.136

Cited by 68 publications

(56 citation statements)

References 14 publications

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“…In spite of the different local geometries around the end and the inner monomers their displacement distributions are identical at both short and long times (Fig.3). This results is in agreement with MD studies on a 2D glassforming alloy showing that having a larger Voronoi volume does not cause a particle to exhibit larger amplitude fluctuations in position [87].…”

Section: B Local Geometry: Voronoi Polyhedrasupporting

confidence: 91%

Cage rattling does not correlate with the local geometry in molecular liquids

Bernini

Puosi

Leporini

2015

Journal of Non-Crystalline Solids

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Molecular-dynamics simulations of a liquid of short linear molecules have been performed to investigate the correlation between the particle dynamics in the cage of the neighbors and the local geometry. The latter is characterized in terms of the size and the asphericity of the Voronoi polyhedra. The correlation is found to be poor. In particular, in spite of the different Voronoi volume around the end and the inner monomers of a molecule, all the monomers exhibit coinciding displacement distribution when they are caged (as well as at longer times during the structural relaxation). It is concluded that the fast dynamics during the cage trapping is a non-local collective process involving monomers beyond the nearest neighbours.PACS numbers:

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Section: B Local Geometry: Voronoi Polyhedrasupporting

confidence: 91%

Cage rattling does not correlate with the local geometry in molecular liquids

Bernini

Puosi

Leporini

2015

Journal of Non-Crystalline Solids

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“…All in all, Fig. 9 confirms that the VP volume is of modest interest [21,109]. One disappointing conclusion drawn by both Fig.8 and Fig.9 is that the increase of the mobility with either the cage size or asphericity is state dependent.…”

Section: Subset Distributions Of Iso-relaxation Statesmentioning

confidence: 57%

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

Bernini

Puosi

Leporini

2015

The Journal of Chemical Physics

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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 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 suggest that the particle fast dynamics is affected by regions beyond the first neighbours, thus supporting the presence of collective, extended fast modes.

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“…To characterize the magnitude of the z-component of the translational displacement of water molecules as a function of their position along the z-axis, we calculated the local Debye-Waller factor for particle i at a short amount of time by 70 DW…”

Section: Resultsmentioning

confidence: 99%

Temperature Dependence of Dimerization and Dewetting of Large-Scale Hydrophobes: A Molecular Dynamics Study

2008

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We studied by molecular dynamics simulations the temperature dependence of hydrophobic association and drying transition of large-scale solutes. Similar to the behavior of small solutes, we found the association process to be characterized by a large negative heat capacity change. The origin of this large change in heat capacity is the high fragility of hydrogen bonds between water molecules at the interface with hydrophobic solutes; an increase in temperature breaks more hydrogen bonds at the interface than in the bulk. With increasing temperature, both entropy and enthalpy changes for association strongly decrease, while the change in free energy weakly varies, exhibiting a small minimum at high temperatures. At around T ) T s ) 360 K, the change in entropy is zero, a behavior similar to the solvation of small nonpolar solutes. Unexpectedly, we find that at T s , there is still a substantial orientational ordering of the interfacial water molecules relative to the bulk. Nevertheless, at this point, the change in entropy vanishes due to a compensating contribution of translational entropy. Thus, at T s , there is rotational order and translational disorder of the interfacial water relative to bulk water. In addition, we studied the temperature dependence of the drying-wetting transition. By calculating the contact angle of water on the hydrophobic surface at different temperatures, we compared the critical distance observed in the simulations with the critical distance predicted by macroscopic theory. Although the deviations of the predicted from the observed values are very small (8-23%), there seems to be an increase in the deviations with an increase in temperature. We suggest that these deviations emerge due to increased fluctuations, characterizing finite systems, as the temperature increases.

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Free volume cannot explain the spatial heterogeneity of Debye–Waller factors in a glass-forming binary alloy

Cited by 68 publications

References 14 publications

Cage rattling does not correlate with the local geometry in molecular liquids

Cage rattling does not correlate with the local geometry in molecular liquids

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

Temperature Dependence of Dimerization and Dewetting of Large-Scale Hydrophobes: A Molecular Dynamics Study

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