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2.3 Basic structure types

Pauling rules: understanding polyhedral structures

(2) Negative and positive local charges should be balanced.
(2) Negative and positive local charges should be balanced.

The sum bond valences s should be equal to the
The sum of of bond valences s should be equal to the
ij ij
oxidation state Vdation state V of ion i: Vof ion i: V == ss
oxi i i i i ij ij

Example 1-TiO (Rutile)
2

CN(Ti ) = 6, CN(O ) = 3: s (Ti-O) = 2/3
2-
4+
ij
s (Ti) = 4, s (O) = 2
ij
ij

Example 2 - GaAs (Sphalerite) Example 3 - SrTiO (Perovskite)
3

4+
2+
3-
CN(Ga ) = 4, CN(As ) = 4: s = 3/4 CN(Sr ) = 12, CN(Ti ) = 6,
3+
ij
2-
s (Ga) = 3, s (As) = 3 CN(O ) = 4(Sr) and 2(Ti)
ij
ij
s (Sr-O) = 1/6 , s (Ti-O) = 2/3
ij
ij