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Nonequilibrium viscosity of glass

机译：玻璃非平衡粘度

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摘要

Since glass is a nonequilibrium material, its properties depend on both composition and thermal history. While most prior studies have focused on equilibrium liquid viscosity, an accurate description of nonequilibrium viscosity is essential for understanding the low temperature dynamics of glass. Departure from equilibrium occurs as a glass-forming system is cooled through the glass transition range. The glass transition involves a continuous breakdown of ergodicity as the system gradually becomes trapped in a subset of the available configurational phase space. At very low temperatures a glass is perfectly nonergodic (or "isostruc-tural"), and the viscosity is described well by an Arrhenius form. However, the behavior of viscosity during the glass transition range itself is not yet understood. In this paper, we address the problem of glass viscosity using the enthalpy landscape model of Mauro and Loucks [Phys. Rev. B 76, 174202 (2007)] for selenium, an elemental glass former. To study a wide range of thermal histories, we compute nonequilibrium viscosity with cooling rates from 10~(-12) to 10~(12) K/s. Based on these detailed landscape calculations, we propose a simplified phenomenological model capturing the essential physics of glass viscosity. The phenomenological model incorporates an ergodicity parameter that accounts for the continuous breakdown of ergodicity at the glass transition. We show a direct relationship between the nonequilibrium viscosity parameters and the fragility of the supercooled liquid. The nonequilibrium viscosity model is validated against experimental measurements of Corning EAGLE XG™ glass. The measurements are performed using a specially designed beam-bending apparatus capable of accurate nonequilibrium viscosity measurements up to 10~(16) Pa s. Using a common set of parameters, the phenomenological model provides an accurate description of EAGLE XG™ viscosity over the full range of measured temperatures and fictive temperatures.
机译：由于玻璃是一种非平衡材料，因此其性能取决于成分和热历史。虽然大多数先前的研究都集中在平衡液体粘度上，但是非平衡粘度的准确描述对于理解玻璃的低温动力学至关重要。当玻璃形成系统在整个玻璃化转变温度范围内冷却时，就会发生平衡偏离。随着系统逐渐陷入可用构型相空间的子集中，玻璃化转变涉及遍历性的连续破坏。在非常低的温度下，玻璃是完全非遍历的（或“同质结构的”），并且粘度通过阿伦尼乌斯形式很好地描述。然而，尚不了解玻璃化转变范围内的粘度行为。在本文中，我们使用Mauro和Loucks [Phys。 B 76，174202（2007）修订版]硒，一种元素玻璃形成剂。为了研究广泛的热历史，我们计算了冷却速度为10〜（-12）到10〜（12）K / s时的非平衡粘度。基于这些详细的景观计算，我们提出了一种简化的现象学模型，用于捕获玻璃粘度的基本物理原理。现象学模型结合了遍历性参数，该参数说明了玻璃化转变时遍历性的连续分解。我们显示了非平衡粘度参数和过冷液体的脆性之间的直接关系。通过康宁EAGLE XG™玻璃的实验测量验证了非平衡粘度模型。使用专门设计的光束弯曲设备进行测量，该设备能够精确测量高达10〜（16）Pa s的非平衡粘度。现象学模型使用一组通用参数，可以在整个测量温度和虚拟温度范围内准确描述EAGLE XG™粘度。

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  • 来源
    《Physical review》 |2009年第9期|094204.1-094204.18|共18页
  • 作者

    John C. Mauro; Douglas C. Allan; Marcel Potuzak;

  • 作者单位

    Science and Technology Division, Corning Incorporated, Corning, New York 14831, USA;

    Science and Technology Division, Corning Incorporated, Corning, New York 14831, USA;

    Science and Technology Division, Corning Incorporated, Corning, New York 14831, USA;

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  • 正文语种 eng
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  • 关键词

    glasses; time-dependent properties; relaxation;

    机译：眼镜;时间相关的属性;松弛;

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