  We describe simulations of active Brownian particles carried out to explore
how dynamics and clustering are influenced by particle shape. Our particles are
composed of four disks, held together by springs, whose relative size can be
varied. These compound objects can be tuned smoothly from having a concave to a
convex surface. We show that even two of these composite particles can exhibit
collective motion modifying the effective Peclet number. We then investigate
how particle geometry can be used to explain the phase behaviour of many such
particles.
