  Synthetic driving force molecular dynamics simulations were utilized to
survey grain boundary mobility in three classes of incoherent {\Sigma}3 twin
boundaries: <112>, <110>, and <111> tilt boundaries. These boundaries are
faceted on low energy planes, and step flow boundary motion occurs by glide of
the triplets of partial dislocations that comprise the mobile facets.
Systematic trends with inclination angle are identified and characterized.
Observations of thermally activated, anti-thermal, and athermal motion are
explained in terms of the orientation of the Shockley partial dislocations
along close-packed and non-close-packed directions. Thermally activated
boundaries follow a compensation effect associated with a facet roughening
transition. As for all faceting boundaries, system size and driving force must
be chosen with care to prevent simulation artifacts.
