  Using Wannier functions to represent the density functional results we
calculate the hybridization corrections to the orbital momentum operator in the
Os 5d shell of Mott insulators Ba2NaOsO6 and Ba2YOsO6. The g-factors are
obtained by evaluating the spin and orbital momentum operators in the atomic
ground states of the Os ion. While the hybridization corrections play minor
role in d3 ion of Ba2YOsO6 with dominant spin moment, they are instrumental for
observation of non- zero g-factor of the d1 ions of Ba2NaOsO6. In addition we
analyze the exchange interactions in Ba2YOsO6 and find them consistent with the
reported magnetic structure.
