X-ray scattering

1. Jun 13, 2005

thearny

Could anyone tell me what the difference between Q-spacing Bragg-spacing D-spacing and repeat distance is? I've always thought that they were same, but seemingly not? What is the realtionship, what is Q?

Its keeping me up at night!

2. Jun 14, 2005

Gokul43201

Staff Emeritus
d-spacing is simply the interplanar distance in a crystal. In this context, the Q-spacing is the length of a reciprocal lattice vector (you have a Bragg peak when the wave vector of the radiation used matches a reciprocal lattice vector). The Bragg-spacing is any distance over which a system is translationally invariant in some direction, and will hence produce a Bragg peak. So, in a crystal, the bragg spacing will be the d-spacing itself. In an superalloy, you will see an adiitional larger (but weaker) Bragg peak giving rise to an additional Bragg spacing. Likewise, you can have a Bragg spacing for a polymer and even a liquid crystal.

The relationship between reciprocal lattice vectors and real lattice vectors depends on the type of Bravais lattice involved.

Last edited: Jun 14, 2005