Phase diagram of the Heisenberg-Kitaev model atT=0

We use series expansions to investigate the zero-temperature phase diagram of the Heisenberg-Kitaev model. Our work confirms the presence of four distinct magnetically ordered phases, identified in recent work, and provides accurate values of the ground state energy and order parameter throughout. We call into question the previous estimates of the location of phase boundaries, and provide an analytic argument for their location.