  In the last two decades, many phase-field models for solid-state sintering
have been published. Two groups of models have emerged, with and without the
contribution of rigid body motion. This paper first describes the previously
published phase-field model with an advection term driven by rigid body motion.
The model is then used to investigate the differences between models with and
without rigid body motion in new benchmark geometries exhibiting markedly
different behavior. Sensitivity studies concerning the parameters of the
rigid-body motion model are conducted and their effects on equilibrium and
kinetic properties explored. In particular, it is shown by simulations that a
shrinkage rate independent of system size requires the inclusion of an
advection term. Finally, the reason behind this behavior is explored and
implications for diffusion-only models are drawn.
