非晶态固体中粘性、扩散和拉伸指数弛豫的剪切转变区理论
Shear-Transformation-Zone Theory of Viscosity, Diffusion, and Stretched Exponential Relaxation in Amorphous Solids
摘要：
剪切转变区（STZ）理论在解释非晶系统在其玻璃化温度$T_g$附近的宽峰值、频率依赖性粘弹性响应方面取得了显著的成功。这一成功是基于该理论的第一原理预测的范围广泛的内部STZ转换率。在这里，我表明，STZ速率分布导致牛顿粘度是强烈的温度依赖性，我建议，它是这种温度依赖性，而不是任何不均匀性引起的扩散增强，这是负责斯托克斯-爱因斯坦违反附近$T_g$。我还表明，拉伸指数松弛的密度波动出现自然从相同的分布STZ过渡率预测的粘弹性行为。然而，为了与$T_g$附近的菲克扩散观测结果保持一致，基于STZ的扩散理论必须以某种方式包括在低温数值模拟中看到的相关位移事件的级联。
英文摘要：
The shear-transformation-zone (STZ) theory has been remarkably successful in accounting for broadly peaked, frequency-dependent, viscoelastic responses of amorphous systems near their glass temperatures $T_g$. This success is based on the theory's first-principles prediction of a wide range of internal STZ transition rates. Here, I show that the STZ rate-distribution causes the Newtonian viscosity to be strongly temperature dependent; and I propose that it is this temperature dependence, rather than any heterogeneity-induced enhancement of diffusion, that is responsible for Stokes-Einstein violations near $T_g$. I also show that stretched-exponential relaxation of density fluctuations emerges naturally from the same distribution of STZ transition rates that predicts the viscoelastic behavior. To be consistent with observations of Fickian diffusion near $T_g$, however, an STZ-based diffusion theory somehow must include the cascades of correlated displacement events that are seen in low-temperature numerical simulations.
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