Department of Materials Science and Engineering, University of Arizona, 4715 E. Fort Lowell Road, Tucson, Arizona 85712, USA.
J Chem Phys. 2013 Jun 28;138(24):244504. doi: 10.1063/1.4811488.
The relaxation behavior of glass is influenced by the presence of dynamical heterogeneities, which lead to an intrinsically non-monotonic decay of fluctuations in density and enthalpy during isothermal annealing. This is apparently a universal feature of fragile glass forming systems associated with localized spatial variations in relaxation time. Here we present direct experimental observation of the nonmonotonic evolution of enthalpy fluctuations in glassy selenium annealed near room temperature. The nonmonotonic change in the distribution of enthalpy fluctuations measured by heat capacity spectroscopy offers direct evidence for the presence of dynamical heterogeneity in this glass. An enthalpy landscape model of selenium is then used to simulate annealing under identical conditions. The simulation results closely follow the evolution of enthalpy fluctuations observed experimentally. The close match between model and experiment demonstrate that enthalpy and density fluctuations are sources of dynamical heterogeneities in glassy materials.
玻璃的弛豫行为受到动力学非均匀性的影响，这导致在等温退火过程中密度和焓的涨落呈固有非单调衰减。这显然是与弛豫时间局部空间变化相关的脆弱玻璃形成系统的普遍特征。在这里，我们直接观察到了在室温附近退火的玻璃态硒中焓涨落的非单调演化的实验观察。通过热容光谱法测量的焓涨落分布的非单调变化为该玻璃中存在动力学非均匀性提供了直接证据。然后，使用硒的焓景观模型来模拟相同条件下的退火。模拟结果与实验中观察到的焓涨落的演化非常吻合。模型与实验之间的紧密匹配表明，焓和密度涨落是玻璃材料中动力学非均匀性的来源。
