  Atomistic simulations provide the most detailed picture of grain boundary
(GB) migration currently available. Nevertheless, extracting unit mechanisms
from atomistic simulation data is difficult because of the zoo of competing,
geometrically complex 3D atomic rearrangement processes. In this work, we
introduce the displacement texture characterization framework for analyzing
atomic rearrangement events during GB migration, combining ideas from slip
vector analysis, bicrystallography and optimal transportation. Two types of
decompositions of displacement data are described: the shear-shuffle and
min-shuffle decomposition. The former is used to extract shuffling patterns
from shear coupled migration trajectories and the latter is used to analyze
temperature dependent shuffling mechanisms. As an application of the
displacement texture framework, we characterize the GB geometry dependence of
shuffling mechanisms for a crystallographically diverse set of mobile GBs in
FCC Ni bicrystals. Two scientific contributions from this analysis include 1)
an explanation of the boundary plane dependence of shuffling patterns via
metastable GB geometry and 2) a taxonomy of multimodal constrained GB migration
mechanisms which may include multiple competing shuffling patterns, period
doubling effects, distinct sliding and shear coupling events, and GB self
diffusion.
