Roles of icosahedral and crystal-like order in the hard spheres glass transition

Abstract

A link between structural ordering and slow dynamics has recently attracted much attention from the context of the origin of glassy slow dynamics. Candidates for such structural order are icosahedral, exotic amorphous and crystal-like. Each type of order is linked to a different scenario of glass transition. Here we experimentally access local structural order in polydisperse hard spheres by particle-level confocal microscopy. We identify the key structures as icosahedral and FCC-like order, both statistically associated with slow particles. However, when approaching the glass transition, the icosahedral order does not grow in size, whereas crystal-like order grows. It is the latter that governs the dynamics and is linked to dynamic heterogeneity. This questions the direct role of the local icosahedral ordering in glassy slow dynamics and suggests that the growing length scale of structural order is essential for the slowing down of dynamics and the non-local cooperativity in particle motion.

Monte Carlo simulations of densely-packed athermal polymers in the bulk and under confinement

“…It is now wellestablished that the face-centered cubic (fee) is marginally thermodynamically more stable than the hexagonal close packed (hep) crystal structure (Bolhuis et al, 1997;Woodcock, 1997). In spite of this, different ordered morphologies can also be observed in experiments and simulations like the random hexagonal close packed (rhep) layered structure or close packed crystallites, randomly oriented with defects being strongly correlated with twinning planes Auer and Frenkel, 2001;Bagley, 1970;Bolhuis et al, 1997;Cheng et al, 2002;Frenkel, 1999;Harland and van Megen, 1997;He et al, 1997;Henderson and van Megen, 1998;Karayiannis et al, 2011Karayiannis et al, , 2012Kawasaki and Tanaka, 2010;Leocmach and Tanaka, 2012;O'Malley and Snook, 2003;Pusey and Vanmegen, 1986;Pusey et al, 1989Pusey et al, , 2009Rintoul and Torquato, 1996;Russo and Tanaka, 2012;Schilling et al, 2010;Zaccarelli et al, 2009). These later crystal structures can be viewed, according to Ostwald's rule (Ostwald, 1897), as intermediate (metastable) thermodynamic stages between the amorphous (random) state and the fee crystal.…”

Decorrelation of the static and dynamic length scales in hard-sphere glass formers

“…Proposals for unveiling such a nontrivial static length include measures of the spatial extension of some locally preferred structure, as obtained from static correlations of a bond-orientational order parameter [7][8][9][10][11][12][13][14][15][16][17] or, via dimensional analysis, from the occurrence frequency of a given local arrangement [18][19][20][21][22][23][24][25][26][27]. Such proposals have long been advocated, but their usefulness remains uncertain [28,29].…”

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

“…This includes the Adam-Gibbs derivation of the structural relaxation [7,8] built on the thermodynamic notion of the configurational entropy [9] -, the mode-coupling theory [10] and extensions [11], the random first-order transition theory (RFOT) [12], the frustrationbased approach [13], as well as the so-called elastic models [14,15]. The search of a link between structural ordering and slow dynamics motivated several studies in liquids [16][17][18][19], colloids [20][21][22] and polymeric systems [20,[23][24][25][26][27][28].…”