  We compare the macroscopic and the local plastic behavior of a model
amorphous solid based on two radically different numerical descriptions. On the
one hand, we simulate glass samples by atomistic simulations. On the other, we
implement a mesoscale elasto-plastic model based on a solid-mechanics
description. The latter is extended to consider the anisotropy of the yield
surface via statistically distributed local and discrete weak planes on which
shear transformations can be activated. To make the comparison as quantitative
as possible, we consider the simple case of a quasistatically driven
two-dimensional system in the stationary flow state and compare mechanical
observables measured on both models over the same length scales. We show that
the macroscale response, including its fluctuations, can be quantitatively
recovered for a range of elasto-plastic mesoscale parameters. Using a newly
developed method that makes it possible to probe the local yield stresses in
atomistic simulations, we calibrate the local mechanical response of the
elasto-plastic model at different coarse-graining scales. In this case, the
calibration shows a qualitative agreement only for an optimized subset of
mesoscale parameters and for sufficiently coarse probing length scales. This
calibration allows us to establish a length scale for the mesoscopic elements
that corresponds to an upper bound of the shear transformation size, a key
physical parameter in elasto-plastic models. We find that certain properties
naturally emerge from the elasto-plastic model. In particular, we show that the
elasto-plastic model reproduces the Bauschinger effect, namely the
plasticity-induced anisotropy in the stress-strain response. We discuss the
successes and failures of our approach, the impact of different model
ingredients and propose future research directions for quantitative multi-scale
models of amorphous plasticity.
