Next: Atomic Temperatures, Previous: Dynamical Properties of Position, Up: Dynamical Atom Properties

property ::= DYN { ANISOTROPY } { X } { ANISTROPY } { V }

Note: the program will accept the above incorrect speling as well as the normal spelling.

This property specification extracts the anisotropy of the fluctuations. Since the principal axis transformation orders the second moment fluctuations by their size, one can measure the anisotropy of the motion using the following measure:

M2X ------------------------- - 1 2 2 M2Y + M2Z -12 SQRT(-----------) + 10 2

where the second moments are in the principal axis system. For this
measure, isotropic motion will yield an anisotropy of 0; motion along a
single line will yield an anisotropy of 1,000,000,000,000. For large
anisotropies, the measure will roughly yield the ratio of the dominant
motion to the other motions. The anisotropy of `X` specifies the
coordinate anisotropy; the anisotropy of `V` specifies the velocity
anisotropy.