In many materials that contain stereoactive lone pairs, the local distortions due to these lone pairs are correlated over long length scales. These materials are long-range ordered and their structures can be determined using average crystallographic techniques such as Bragg diffraction. In other materials, however, the disortions due to stereoactive lone-pairs are uncorrelated . These materials are crystallographically disordered and average-structure crystallographic methods yield inaccurate high-symmetry structural models. Because the distortion around each cation depends on the relative orientation of the corresponding lone pair, this behaviour can be considered a form of orientational disorder, analogous to molecular or polyanionic orientational disorder as discussed above. These lone-pair effects may also be dynamic, showing fluctations or even rotations of the lone-pair charge density, mirroring the dynamic orientational disorder of "paddlewheel" materials .