To make a glass—avoid the crystal

Palberg, Thomas; Bartsch, E.; Beyer, R. A.; Hofmann, M; Lorenz, Nina; Marquis, Janina; Niu, Ran; Okubo, Tsuneo

doi:10.1088/1742-5468/2016/07/074007

Cited by 8 publications

(17 citation statements)

References 165 publications

(276 reference statements)

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“…A topic of practical importance in many applications is related to how the freezing transition is avoided [165], and what are the factors that determine the glass-forming ability of a material. In Fig.…”

Section: Roles Of Precursors In Vitrificationmentioning

confidence: 99%

Crystal nucleation as the ordering of multiple order parameters

Russo

Tanaka

2016

The Journal of Chemical Physics

107

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Nucleation is an activated process in which the system has to overcome a free energy barrier in order for a first-order phase transition between the metastable and the stable phases to take place. In the liquid-to-solid transition the process occurs between phases of different symmetry, and it is thus inherently a multi-dimensional process, in which all symmetries are broken at the transition. In this Focus Article, we consider some recent studies which highlight the multi-dimensional nature of the nucleation process. Even for a single-component system, the formation of solid crystals from the metastable melt involves fluctuations of two (or more) order parameters, often associated with the decoupling of positional and orientational symmetry breaking. In other words, we need at least two order parameters to describe the free-energy of a system including its liquid and crystalline states. This decoupling occurs naturally for asymmetric particles or directional interactions, focusing here on the case of water, but we will show that it also affects spherically symmetric interacting particles, such as the hard-sphere system. We will show how the treatment of nucleation as a multi-dimensional process has shed new light on the process of polymorph selection, on the effect of external fields on the nucleation process, and on glass-forming ability.

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Section: Roles Of Precursors In Vitrificationmentioning

confidence: 99%

Crystal nucleation as the ordering of multiple order parameters

Russo

Tanaka

2016

The Journal of Chemical Physics

107

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“…Consequently, the maximum relative undercooling, ∆T R = T L -T n /T L (T L liquidus and T n nucleation temperature) of these alloys are by a factor of two smaller than the typical relative undercooling of metals The situation again changes, if glass-forming alloys are studied. As a side-remark, this topic has also been extensively studied in colloidal glass formers [111]. In both system classes, glass formation requires the avoidance of crystal nucleation.…”

Section: Short Range Order In the Undercooled Liquid State Of Pure Mementioning

confidence: 99%

Overview: Experimental studies of crystal nucleation: Metals and colloids

Herlach

Palberg

Klassen

et al. 2016

The Journal of Chemical Physics

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Crystallization is one of the most important phase transformations of first order. In the case of metals and alloys, the liquid phase is the parent phase of materials production. The conditions of the crystallization process control the as-solidified material in its chemical and physical properties. Nucleation initiates the crystallization of a liquid. It selects the crystallographic phase, stable or meta-stable. Its detailed knowledge is therefore mandatory for the design of materials. We present techniques of containerless processing for nucleation studies of metals and alloys. Experimental results demonstrate the power of these methods not only for crystal nucleation of stable solids but in particular also for investigations of crystal nucleation of metastable solids at extreme undercooling. This concerns the physical nature of heterogeneous versus homogeneous nucleation and nucleation of phases nucleated under non-equilibrium conditions. The results are analyzed within classical nucleation theory that defines the activation energy of homogeneous nucleation in terms of the interfacial energy and the difference of Gibbs free energies of solid and liquid. The interfacial energy acts as barrier for the nucleation process. Its experimental determination is difficult in the case of metals. In the second part of this work we therefore explore the potential of colloidal suspensions as model systems for the crystallization process. The nucleation process of colloids is observed in situ by optical observation and ultra-small angle X-ray diffraction using high intensity synchrotron radiation. It allows an unambiguous discrimination of homogeneous and heterogeneous nucleation as well as the determination of the interfacial free energy of the solid-liquid interface. Our results are used to construct Turnbull plots of colloids, which are discussed in relation to Turnbull plots of metals and support the hypothesis that colloids are useful model systems to investigate crystal nucleation.

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“…The case of charged particles interacting via long-ranged Coulombic potentials has been explored by MCT with a predicted vitrified phase as a result 9 . For several systems of charged col- loids, a glassy phase, or Wigner glass, has been identified, including charged polystyrene particles 10 and highly charged clay platelets [11][12][13][14][15][16][17] . In all of these experiments, scattering methods have been used to probe the often complex ensemble-averaged sample dynamics.…”

Section: Introductionmentioning

confidence: 99%

Linking slow dynamics and microscopic connectivity in dense suspensions of charged colloids

et al. 2018

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The quest to unravel the nature of the glass transition, where the viscosity of a liquid increases by many orders of magnitude, while its static structure remains largely unaffected, remains unresolved. While various structural and dynamical precursors to vitrification have been identified, a predictive and quantitative description of how subtle changes at the microscopic scale give rise to the steep growth in macroscopic viscosity is missing. It was recently proposed that the presence of long-lived bonded structures within the liquid may provide the long-sought connection between local structure and global dynamics. Here we directly observe and quantify the connectivity dynamics in liquids of charged colloids en route to vitrification using three-dimensional confocal microscopy. We determine the dynamic structure from the real-space van Hove correlation function and from the particle trajectories, providing upper and lower bounds on connectivity dynamics. Based on these data, we extend Dyre's model for the glass transition to account for particle-level structural dynamics; this results in a microscopic expression for the slowing down of relaxations in the liquid that is in quantitative agreement with our experiments. These results indicate how vitrification may be understood as a dynamical connectivity transition with features that are strongly reminiscent of rigidity percolation scenarios.

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To make a glass—avoid the crystal

Cited by 8 publications

References 165 publications

Crystal nucleation as the ordering of multiple order parameters

Crystal nucleation as the ordering of multiple order parameters

Overview: Experimental studies of crystal nucleation: Metals and colloids

Linking slow dynamics and microscopic connectivity in dense suspensions of charged colloids

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