Left: radio power at 1.4 GHz versus the cluster X-ray luminosity in the 0.1−2.4 keV band. Full dots are observed clusters taken from the recent compilations by Feretti et al. (2012) and Govoni et al. (2012); green triangles are the simulated clusters R1a, R2, and R6 from Xu et al. (2012). In these simulations L_X and L_1.4  GHz have been calculated within a circle of 1 Mpc in radius. Right: azimuthally averaged radio-halo brightness profiles of the total intensity I (green dots), polarized intensity P (red squares), and fractional polarization FPOL = (blue triangles) of the clusters R1a (solid lines), R2 (dashed lines), and R6 (dotted lines).