CiteULike: weeks' Stillinger

Interfacial Density Profile for Fluids in the Critical Region

FP Buff — 2008-03-03T21:04:06-00:00

Physical Review Letters, Vol. 15, No. 15. (11 October 1965), pp. 621-623.

Optimal Packings of Superdisks and the Role of Symmetry

Y Jiao — 2008-07-20T23:49:53-00:00

Physical Review Letters, Vol. 100, No. 24. (2008)

Almost all studies of the densest particle packings consider convex particles. Here, we provide exact constructions for the densest known two-dimensional packings of superdisks whose shapes are defined by |x1|2p+|x2|2p1 and thus contain a large family of both convex (p0.5) and concave (0<p<0.5) particles. Our candidate maximal packing arrangements are achieved by certain families of Bravais lattice packings, and the maximal density is nonanalytic at the “circular-disk” point (p=1) and increases dramatically as p moves away from unity. Moreover, we show that the broken rotational symmetry of superdisks influences the packing characteristics in a nontrivial way.

Reply to “Comment on `Translation-rotation paradox for diffusion in fragile glass-forming liquids' ”

Frank Stillinger — 2007-05-16T17:50:04-00:00

Physical Review E, Vol. 53, No. 3. (March 1996), pp. 2995-2997.

We discuss several aspects of the fluidized domain model advanced earlier to explain rotational and translational diffusion rates for fragile glass formers and; in particular; we point out weaknesses in the preceding Comment [Sillescu; Phys. Rev. E 53 ; 2992 (1996)]. Recent experimental results are cited to refine estimates of domain characteristics for orthoterphenyl at T g and to suggest that domain heterogeneity in space and time underlies stretched exponential relaxation behavior for rotational motion. © 1996 The American Physical Society.

Computational probes of molecular motion in the Lewis-Wahnström model for ortho-terphenyl

Thomas Lombardo — 2007-05-15T20:53:34-00:00

The Journal of Chemical Physics, Vol. 125, No. 17. (2006), pp. 174507-174507.

We use molecular dynamics simulations to investigate translational and rotational diffusion in a rigid three-site model of the fragile glass former ortho-terphenyl, at 260 KT346 K and ambient pressure. An Einstein formulation of rotational motion is presented, which supplements the commonly used Debye model. The latter is shown to break down at supercooled temperatures as the mechanism of molecular reorientation changes from small random steps to large infrequent orientational jumps. We find that the model system exhibits non-Gaussian behavior in translational and rotational motion, which strengthens upon supercooling. Examination of particle mobility reveals spatially heterogeneous dynamics in translation and rotation, with a strong spatial correlation between translationally and rotationally mobile particles. Application of the Einstein formalism to the analysis of translation-rotation decoupling results in a trend opposite to that seen in conventional approaches based on the Debye formalism, namely, an enhancement in the effective rate of rotational motion relative to translation upon supercooling. ©2006 American Institute of Physics

Translation-rotation paradox for diffusion in fragile glass-forming liquids

Frank Stillinger — 2007-04-01T03:01:19-00:00

Physical Review E, Vol. 50, No. 3. (1994), pp. 2064-2068.

Translational and rotational diffusion rates in low-molecular-weight liquids tend to conform well to the predictions of the classic Stokes-Einstein-Debye model if temperature T is not too low. Specifically; the diffusion constants D trans and D rot are proportional to T /η( T ); where η is the shear viscosity. However; fragile glass formers seem to present a paradox: near the glass transition temperature T g this proportionality continues for D rot ; but D trans can be enhanced by 10 2 . A ‘‘fluidized domain’’ model is proposed to explain these observations. Owing to a suitable combination of domain parameters (mean size; lifetime; concentration; internal viscosity); the observed diffusion rate discrepancy can indeed be rationalized. Rough estimates for these domain parameters are provided for two fragile glass formers (orthoterphenyl and 1;3;5-tri-α-naphthyl benzene) at their respective T g ’s.

Comment on `Jamming at zero temperature and zero applied stress: The epitome of disorder'

Aleksandar Donev — 2007-09-27T03:04:22-00:00

Physical Review E, Vol. 70, No. 4. (2004), pp. 043301-043301.

O'Hern, Silbert, Liu, and Nagel [Phys. Rev. E. 68, 011306 (2003)] claim that a special point J of a "jamming phase diagram" (in density, temperature, stress space) is related to random close packing of hard spheres and that it represents, for their suggested definitions of jammed and random, the recently introduced maximally random jammed state. We point out several difficulties with their definitions and question some of their claims. Furthermore, we discuss the connections between their algorithm and other hard-sphere packing algorithms in the literature.

A Topographic View of Supercooled Liquids and Glass Formation

Frank Stillinger — 2007-05-19T22:04:07-00:00

Science, Vol. 267, No. 5206. (31 March 1995), pp. 1935-1939.

Various static and dynamic phenomena displayed by glass-forming liquids, particularly those near the so-called "fragile" limit, emerge as manifestations of the multidimensional complex topography of the collective potential energy function. These include non-Arrhenius viscosity and relaxation times, bifurcation between the [agr]- and [beta]-relaxation processes, and a breakdown of the Stokes-Einstein relation for self-diffusion. This multidimensional viewpoint also produces an extension of the venerable Lindemann melting criterion and provides a critical evaluation of the popular "ideal glass state" concept. 10.1126/science.267.5206.1935