Rodriguez Fris J A, Alarcón L M, Appignanesi G A
Fisicoquímica, Departamento de Química, Universidad Nacional del Sur, Avenida Alem 1253, 8000 Bahía Blanca, Argentina.
Phys Rev E Stat Nonlin Soft Matter Phys. 2007 Jul;76(1 Pt 1):011502. doi: 10.1103/PhysRevE.76.011502. Epub 2007 Jul 2.
Recent investigations have demonstrated that the short-time fluctuations in a supercooled liquid can be used as predictors of the long-time dynamic propensity (that is, the regions of the sample with enhanced tendency to be mobile within time scales on the order of the alpha -relaxation time). This could mean that the long-time dynamics (the actual mobility of the particles at such long times) would be implicit in the short-time dynamics or else, that the long-time dynamic propensity [as defined in A. Widmer-Cooper and P. Harrowell, Phys. Rev. Lett. 96, 185701 (2006)], while providing a measure of the degree of jamming of the local structure, would only be sensitive to the short time behavior. The first scenario is in clear disagreement with our recent finding that the influence of the local structure on dynamics (as determined by the propensity for motion) is only local in time, fading out at times close to the metabasin lifetime, much before the alpha -relaxation time. Thus, in this work we show that the short-time fluctuations in supercooled liquids do in fact represent precursors to the dynamics at intermediate times commensurate with the metabasin lifetime (being thus able to predict the regions of the sample that will present high propensity for motion at such stage) but that the dynamical behavior at later times of the alpha relaxation is unpredictable, in agreement with a metabasin random walk scenario.
最近的研究表明，过冷液体中的短时间涨落可被用作长时间动力学倾向的预测指标（即样品中在与α弛豫时间量级相当的时间尺度内具有增强的移动倾向的区域）。这可能意味着长时间动力学（粒子在如此长的时间内的实际移动性）隐含在短时间动力学中，或者说，长时间动力学倾向[如A. Widmer-Cooper和P. Harrowell在《物理评论快报》96, 185701 (2006)中所定义]，虽然提供了局部结构的堵塞程度的一种度量，但仅对短时间行为敏感。第一种情况与我们最近的发现明显不符，即局部结构对动力学的影响（由运动倾向决定）在时间上只是局部的，在接近亚稳态寿命时逐渐消失，远早于α弛豫时间。因此，在这项工作中我们表明，过冷液体中的短时间涨落实际上确实代表了与亚稳态寿命相当的中间时间的动力学的先兆（从而能够预测样品中在该阶段将呈现高移动倾向的区域），但α弛豫后期的动力学行为是不可预测的，这与亚稳态随机游走的情况一致。
