Shear-induced overaging in a polymer glass

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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 increases in relaxation times Δτ₁/₂ rise rapidly with deformation, becoming exponential in the plastic regime. This ``overaging'' is distinct from standard aging. We find increases in pressure, bond-orientational order and in the average energy of the inherent structures (<eIS>) 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''