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吉野 元@阪大サイバー
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2017年11月28日(火) 16:30 - 大阪大学豊中キャンパス サイバーメディアセンター7F会議室
http://www.cp.cmc.osaka-u.ac.jp
Paddy Royall 氏 (Univ. Bristol)
Attacking the Glass Problem by Getting Low in the Energy Landscape:
Nano-Particle Resolved Studies and Large Deviations
Our understanding of the mechanism by which the viscosity of supercooled
liquids increase by many decades is hampered by the difficulty in
discriminating apparently incompatible theoretical approaches. The
challenge lies in equilibrating samples at sufficient supercooling that
experimental or numerical techniques can probe suitable quantities that
enable the theories to be discriminated, or by directly testing the
theories.
Recently, considerable progress has been made in obtaining data which
can help to discriminate such theories, in both molecular experiments
and simulation [1]. Much of these new data tend to support theories
which imagine a thermodynamic origin of the glass transition - in
contrast to a predominately dynamic one. Of the thermodynamic theories,
we begin by probing the predictions of the geometric frustration theory
of the glass transition [2].
Nevertheless, plenty of compelling evidence in support of dynamic
facilitation (which posits that the glass transition is driven by a
dynamical phase transition) exists [3], which we have shown can be
accessed in experiments [4]. Here we present new results, which use
novel techniques to obtain very deeply supercooled configurations in an
atomistic model glassformer. These naturally lend themselves to a
determination of the dynamical phase transition of facilitation.
Consistent with results on certain lattice models [5], we find that the
dynamical phase transition has a lower temperature bound, which we
interpret as a critical point. Now our deeply supercooled configurations
also give access to the configurational entropy, from which we can
locate the Kauzmann temperature. Remarkably, within the accuracy of our
approach, this point where the thermodynamic theories suggest a phase
transition lies at the same temperature as the lower critical point of
the dynamical transition. We suggest that our findings may lead to a
path to reconcile the competing thermodynamic and dynamic
interpretations of the glass transition [6].
[1] Royall, C. P.; Turci, F.; Tatsumi, S.; Russo, J. & Robinson, J. "The
race to the bottom: approaching the ideal glass?", ArXiV,1711.04739
(2017).
[2] Turci, F.; Tarjus, G. & Royall, C. P. "From Glass Formation to
Icosahedral Ordering by Curving Three-Dimensional Space", Phys. Rev.
Lett., 118, 215501 (2017).
[3] Speck, T.; Malins, A. & Royall, C. P. "First-Order Phase Transition
in a Model Glass Former: Coupling of Local Structure and Dynamics" Phys.
Rev. Lett. 109, 195703 (2012).
[4] Pinchaipat, R.; Campo, M.; Turci, F.; Hallet, J.; Speck, T. &
Royall, C. P. "Experimental Evidence for a Structural-Dynamical
Transition in Trajectory Space" Phys. Rev. Lett., 119, 028004 (2017).
[5] Turner, R. M.; Jack, R. L. & Garrahan, J. P. Overlap and activity
glass transitions in plaquette spin models with hierarchical dynamics
Phys. Rev. E, 92, 022115 (2015).
[6] Turci, F.; Royall, C. P. & Speck, T. Non-Equilibrium Phase
Transition in an Atomistic Glassformer: the Connection to Thermodynamics
Phys. Rev. X, 7 031028 (2017).
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Hajime Yoshino
Associate Professor
Cybermedia Center, Osaka University
1-32 Machikaneyama, Toyonaka
560-0043 Japan
Tel: +81-(0)6-6850-6841
FAX: +81-(0)6-6850-6842
E-mail: yoshino@cmc.osaka-u.ac.jp
http://www.cp.cmc.osaka-u.ac.jp/~yoshino/