  Using Monte Carlo and molecular dynamics simulations, we investigate the
equilibrium phase behavior of a monodisperse system of Mackay icosahedra. We
define the icosahedra as polyatomic molecules composed of a set of
Lennard-Jones subparticles arranged on the surface of the Mackay icosahedron.
The phase diagram contains a fluid phase, a crystalline phase and a rotator
phase. We find that the attractive icosahedral molecules behave similar to hard
geometric icosahedra for which the densest lattice packing and the rotator
crystal phase have been identified before. We show that both phases form under
attractive interactions as well. When heating the system from the dense crystal
packing, there is first a transition to the rotator crystal and then another to
a fluid phase.
