# Debye-Waller factor

From Christoph's Personal Wiki

The **Debye-Waller factor**, also known as the **B-factor** or the **temperature factor** describes the decrease in scattering intensity (either from x-ray or neutron scattering) due to the thermal motion of the atoms, or due to crystal disorder. The thermal motion, or disorder, in some sense reduces the validity of the Laue diffraction condition which is based on fixed atoms.

I = I_0 * exp(-1/3 * |G|^2 * u^2)

I is the weakened intensity and I_{0} the source intensity. G is a reciprocal lattice vector and u the thermally enhanced oscillation amplitude of the atoms.

Higher orders of Bragg reflection are weakened more.

## Restrictions

Normally, the following restrictions apply to the anisotropic B-factor tensor

Triclinic | none |

Monoclinic | B13 = B23 = 0 when β = α = 90° B12 = B23 = 0 when γ = α = 90° |

Orthorhombic | B12 = B13 = B23 = 0 |

Tetragonal | B11 = B22 and B12 = B13 = B23 = 0 |

Rhombohedral | B11 = B22 = B33 and B12 = B13 = B23 |

Hexagonal | B11 = B22 and B13 = B23 = 0 |

Cubic | B11 = B22 = B33 and B12 = B13 = B23 = 0 |