We couple the recently developed self-learning metabasin escape algorithm,which enables efficient exploration of the potential energy surface (PES), withshear deformation to elucidate strain-rate and temperature effects on the sheartransformation zone (STZ) characteristics in two-dimensional amorphous solids.In doing so, we report a transition in the STZ characteristics that can beobtained through either increasing the temperature or decreasing the strainrate. The transition separates regions having two distinct STZ characteristics.Specifically, at high temperatures and high strain rates, we show that the STZshave characteristics identical to those that emerge from purely strain-driven,athermal quasistatic atomistic calculations. At lower temperatures andexperimentally relevant strain rates, we use the newly coupled PES + sheardeformation method to show that the STZs have characteristics identical tothose that emerge from a purely thermally activated state. The specific changesin STZ characteristics that occur in moving from the strain-driven to thermallyactivated STZ regime include a 33% increase in STZ size, faster spatial decayof the displacement field, a change in the deformation mechanism inside the STZfrom shear to tension, a reduction in the stress needed to nucleate the firstSTZ, and finally a notable loss in characteristic quadrupolar symmetry of thesurrounding elastic matrix that has previously been seen in athermal,quasistatic shear studies of STZs.
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