Phase and Glass Transitions in Short-Range Central Potential Model Systems:  The Case of C₆₀

Abstract

Extensive molecular dynamics simulations show that a short-range central potential, suited to model C60, undergoes a high temperature transition to a glassy phase characterized by the positional disorder of the constituent particles. Crystallization, melting, and sublimation, which also take place during the simulation runs, are illustrated in detail. It turns out that vitrification and the mentioned phase transitions occur when the packing fraction of the system-defined in terms of an effective hard-core diameter-equals that of hard spheres at their own glass and melting transition, respectively. A close analogy also emerges between our findings and recent mode coupling theory calculations of structural arrest lines in a similar model of protein solutions. We argue that the conclusions of the present study might hold for a wide class of potentials currently employed to mimic interactions in complex fluids (some of which are of biological interest), suggesting how to achieve at least qualitative predictions of vitrification and crystallization in those systems.

Glass transition in fullerenes: Mode-coupling theory predictions

“…Our results are readily testable using molecular-dynamics computer simulation, such as performed recently [30,31,32].…”

C60: The First One-Component Gel?

“…The Girifalco potential is plotted in 1. This Girifalco model is known to undergo dynamical arrest at high temperature and density [25][26][27]. The glass line intersects the gas-liquid spinodal at around T G ≈ 1100 K, while crystallisation is expected at higher temperature [25].…”

Glass Transition Line in C60: A Mode-Coupling/Molecular-Dynamics Study

“…As a consequence, we have deduced in refs [2,3] that the hard-sphere behavior plays the main role in determining the structure of the C 60 glass, which hence results essentially repulsion-driven in nature. In order to reconcile the attractive nature of the MCT glass discussed in ref [19] with the results of refs [2,3] it is worth observing in Figure 5 that in the low temperatures regime the bending of the MD curve is milder, with respect to the MCT predictions. In this case, it could be possible that, on lowering the temperature further, also the glass observed in our previous studies would display a more pronounced attraction-driven effects.…”

“…The onset of a glassy phase characterized by positional disorder in the Girifalco central potential model of C 60 [1] has been recently documented by some of us via Molecular Dynamics (MD) studies [2,3]. Interest in the vitrification process in fullerenes stems not only from the intrinsic relevance of this class of materials, but also from the nature of their interparticle interaction.…”

“…Besides our simulations investigations [2,3], the study of the glass transition line in the Girifalco model has been recently addressed by Greenall and Voigtmann [19]. In ref [19] these authors carry out ideal MCT calculations, using as input data for the theory the static structure factors S(k) obtained from the Hypernetted Chain (HNC) and Percus-Yevick (PY) liquid state theories [20].…”