Quadratic elongation: a quantitative measure of distortion in coordination polyhedra.
Quadratic elongation and the variance of bond angles are linearly correlated for distorted octahedral and tetrachedral corrdination complexes, both of which show variations in bond length and bond angle. The quadratic elongation is dimensionless, giving a quantitative measure of polyhedral disortion which is independent of the effective size of the polyhedron.
Robinson
K
K
Gibbs
G V
GV
Ribbe
P H
PH