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freakJoe

Second Pauling’s Rule

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freakJoe    0

I have problem with those tasks, i was reading about rule, but still have no idea what to do...

 

1) FeTiO3 (mineral Ilmenite) possesses the corundum structure (remember our
discussion in the class) – an hcp array of oxides with cations filling 2/3 of octahedral holes.
Use the bond valence rules (Second Pauling’s Rule) to decide which oxidation states are
present: Fe(II) Ti(IV) or Fe(III) Ti(III).
Bond Distances (dexp, Å) Tabulated reference values Constants
FeO = 3×2.07 and 3×2.20 R0(FeO) = 1.795 Å b = 0.30
TiO = 3×1.88 and 3×2.09 R0(TiO) = 1.815 Å b = 0.37
Check for oxygen valence (what is the coordination number of O?): each oxygen is bound to
Fe and Ti with both bond distances.)
2) CaWO4 has the scheelite structure where the W6+ ions are tetrahedrally
coordinated. Use the bond valence rules (Second Pauling’s Rule) to decide if the WO4
tetrahedra share corners, i.e. oxygens are bridging, or the WO4 tetrahedra are isolated, i.e.
oxygens are terminal. Show your bond strength calculation.

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