Wallace Matthew L, Joós Béla
Ottawa-Carleton Institute for Physics, University of Ottawa Campus, Ottawa, Ontario, Canada K1N 6N5.
Phys Rev Lett. 2006 Jan 20;96(2):025501. doi: 10.1103/PhysRevLett.96.025501. Epub 2006 Jan 17.
A phenomenon recently coined as overaging implies a slowdown in the collective (slow) relaxation modes of a glass when a transient shear strain is imposed. We are able to reproduce this behavior in simulations of a supercooled polymer melt by imposing instantaneous shear deformations. The increase in relaxation times Delta(tau(1/2)) rises rapidly with deformation, becoming exponential in the plastic regime, and is accompanied by significant changes in the distribution of these relaxation times throughout the system. This overaging is distinct from standard aging. We find increases in pressure, bond-orientational order, and in the average energy of the inherent structures (<e(IS)>) of the system, all dependent on the size of the deformation. The observed change in behavior from elastic to plastic deformation suggests a link to the physics of the "jammed state."
最近新出现的一种现象——过老化，是指当施加瞬态剪切应变时，玻璃态物质的集体（缓慢）弛豫模式会减慢。我们通过施加瞬时剪切变形，能够在过冷聚合物熔体的模拟中重现这种行为。弛豫时间增量Δ(τ(1/2))随着变形迅速增加，在塑性区域呈指数增长，并且伴随着整个系统中这些弛豫时间分布的显著变化。这种过老化与标准老化不同。我们发现系统的压力、键取向序以及固有结构的平均能量(<e(IS)>)均增加，且都取决于变形的大小。观察到的从弹性变形到塑性变形的行为变化表明与“堵塞状态”的物理机制存在联系。
