Beziehungen zwischen Bindungslängen und Bindungsstärken in Oxidstrukturen

Abstract

The vond valencev, which is a measure for bond strengths, was estimated byPauling, 1929¹, as the ratio of charge to coordination number of the cation. For non-regular coordination polyhedra, the bond valence depends strongly on the bond lengthL. Good results are obtained for the following relations ofv vs.L:

$$\upsilon = \left( {\frac{{L(1)}}{L}} \right)^N $$

with exponentsN between 4.0 and 6.0 or

$$L(\upsilon ) = L(1) - 2k log \upsilon $$

with most 2k-values between 0.75 and 1.1 Å.

The bond valence sums are not very sensitive to the values ofN or 2k, resp., but very much to theL (1)-values (length for unit bond valence). Therefore theL (1)-values should be adapted to each structure. Some values ofL (1),N, 2k andL _max are listed. The increase of mean bond lengths with increasing distortion of a coordination polyhedron can be estimated by

$$\bar L = L(\bar \upsilon ) + 2k \log \upsilon /{}^n\sqrt {\upsilon _1 \cdot \upsilon _2 \cdots \upsilon _n \cdot } $$