Ionic radii (Shannon) for 8-coordinate M(III) ion
These are Shannon ionic radii.
The "effective ionic radii" quoted here assume that the ionic radius of F- is 133 pm and that of O2- is 140 pm.
Values depend upon the coordination number and for d-block metals whether or not the metal is in a high or low spin state.
Older "crystal ionic radii" are based upon a radius of six-coordinate F- = 119 pm and are 14-18% larger than effective ionic radii.
You can look at visual representations of the data for different coordination and oxidation numbers using the following links,
- R.D. Shannon, Acta Cryst., 1976, A32, 751.
- R.D. Shannon and C.T. Prewitt, Acta Cryst., 1969, B25, 925.
- R.D. Shannon and C.T. Prewitt, Acta Cryst., 1970, B26, 1046.
- J.E. Huheey, E.A. Keiter, and R.L. Keiter in Inorganic Chemistry : Principles of Structure and Reactivity, 4th edition, HarperCollins, New York, USA, 1993.