ADPs in crystal structures
 
In crystal structures derived from powder diffraction experiments Atomic Displacement Parameters (also known as atomic vibration parameters and thermal parameters) are used to generate displacement ellipsoids.
 
Displacement ellipsoids represent atomic motion and can be either isotropic or anisotropic.  
 
The shape and size of ADPs can be used to highlight potential errors with the data; the smaller and more spherical the ellipses for anisotropic atoms, the better the data.
 
See also:
Cartesian coordinates from CIF file
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