For the Fe-I site the relevant rotation axis is the z-axis.

For the Fe-II site, the relevant rotation axis is the x-axis.

The electric field gradient tensor for each site will depend on this symmetry and will give the information about the orientation of the PAS with respect to the crystal axes. The EFG tensor at the Fe-I site will have three equal diagonal components along the z-axis and two equal diagonal components in the xy-plane. The EFG tensor at the Fe-II site will have two equal diagonal components along this axis and three equal diagonal components in the xy-plane.