What d orbitals are used in the hybridisation of the molecule $\ce{IF7}$. I know the hybrid state of Iodine is $sp^3d^3$ i.e. 3d orbitals are involved in hybridisation.
Some say they are $d_{(xy)}, d_{(yz)}, d_{(zx)}$ and some say $d_{(x^2-y^2)}, d_{(z^2)}$ and $d_{xy}$ are involved? Also what is the theoretical reason for it. Like I know for $sp^3d^2$ hybridisation only $d_{x2-y2}$ and $d_{z^2}$ are involved because they lie along x,y,z axes and so do the hybrid orbitals like in $\ce{SF6}$ each angle is π/2. Is there some theoretical explanation for $\ce{IF7}$ also which has pentagonal bipyramidal shape?
I know a very similar question has already been asked; How can the Bonding in IF7 be explained using LCAO method?
But it says that bonding in $\ce{IF7}$ cannot be predicted as bonds are predominantly ionic plus the answers mentioned there are using very complicated principles and theories which I am unaware of. I only know the basic theories of VSEPR, Valence Bond and the hypothetical concept of hybridisation plus very little Molecular Orbital Theory. May someone explain the bonding in $\ce{IF7}$ in a fairly simple manner especially the d orbitals used in its hybridisation. I am not specifically asking for $\ce{IF7}$ but any molecule showing $sp^3d^3$ hybridisation?
