text: A common simplification to (14) is the harmonic approximation, in which the probability density function is modeled as a Gaussian. Under this approximation, static displacive disorder is ignored and it is assumed that atomic displacements are determined entirely by motion (alternative models in which the Gaussian approximation is invalid have been considered elsewhere).
  From equations (7) and (14), the Debye–Waller factor  contributes to the observed intensity of a diffraction experiment. And based on (16), we see that our anisotropic displacement factor  is responsible for determining . Additionally, (15) shows that  may be directly related to the probability density function  for a nuclear displacement  from the mean position. As a result, its possible to conduct a scattering experiment on a crystal, fit the resulting spectrum for the various atomic  values, and derive each atoms tendency for nuclear displacement from .