  It is well known that the twinning is an important mode of plastic
deformation in nanocrystalline materials. As a result, it is expected that the
twin can interact with different grain boundaries (GBs) during the plastic
deformation. Understanding these twin-GB interactions is crucial for our
understanding of mechanical behavior of materials. In this work, the twin
interaction with different $\Sigma$11 symmetric and asymmetric tilt GBs has
been investigated in BCC Fe using molecular dynamics (MD) simulations. The
results indicate that twin nucleate from the crack or GB and, its interaction
with $\Sigma$11 asymmetric tilt GBs leads to the formation of a new GB. This
new GB consist of $<$100$>$ Cottrell type immobile dislocations. The detailed
atomistic mechanisms responsible for this new GB formation have been revealed
using atomistic simulations. Interestingly, the new GB formation has not been
observed in the case of twin interaction with $\Sigma$11 symmetric tilt GBs.
