Phase field crystal modeling as a unified atomistic approach to defect dynamics
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abstract
Material properties controlled by evolving defect structures, such as
mechanical response, often involve processes spanning many length and time
scales which cannot be modeled using a single approach. We present a variety of
new results that demonstrate the ability of phase field crystal (PFC) models to
describe complex defect evolution phenomena on atomistic length scales and over
long, diffusive time scales. Primary emphasis is given to the unification of
conservative and non- conservative dislocation creation mechanisms in
three-dimensional FCC and BCC materials. These include Frank-Read-type glide
mechanisms involving closed dislocation loops or grain boundaries as well as
Bardeen-Herring-type climb mechanisms involving precipitates, inclusions,
and/or voids. Both source classes are naturally and simultaneously captured at
the atomistic level by PFC de- scriptions, with arbitrarily complex defect
configurations, types, and environments. An unexpected dipole-to-quadrupole
source transformation is identified, as well as various new and complex geomet-
rical features of loop nucleation via climb from spherical particles. Results
for the strain required to nucleate a dislocation loop from such a particle are
in agreement with analytic continuum theories. Other basic features of FCC and
BCC dislocation structure and dynamics are also outlined, and initial results
for dislocation-stacking fault tetrahedron interactions are presented. These
findings together highlight various capabilities of the PFC approach as a
coarse-grained atomistic tool for the study of three-dimensional crystal
plasticity.
