  Capturing twin nucleation in full-field crystal plasticity is a long-standing
problem in materials science. The challenge resides mainly in the biased
regional lattice transformation associated with twin formation in defiance of
its obedience to a threshold stress law which could be fulfilled in regions
where twinning is deferred. Hence, determining a favorable site for nucleation
of a twin variant remains a daunting task. We hypothesized that this
site-specific nucleation is sensitive to the prior atomic structure of the
lattice so twin embryos form in regions where the lattice transformation energy
is minimum. Thus, quantifying the local strain energy required to trigger a
stable twin underscores the non-pseudo-slip behavior of twin nucleation and
growth. We performed atomistic calculations based on the nudged elastic band
method to identify the minimum energy path and activation energy associated
with {10-12} twin nucleation in titanium. Results of calculations demonstrate
that the role of stress and atomic structure in twin nucleation could be
understood in terms of the minimum energy path, energy barrier, and relaxed
energy. Remarkably, for symmetric tilt grain boundaries, a linear correlation
between the nucleation stress and grain boundary energy was observed.
