Q-spacing, Bragg-spacing, D-spacing & Repeat Distances Explained

[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!

 

[Gokul43201]

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.

 

[ravenprp]

Q-spacing, Bragg-spacing, D-spacing, and repeat distance are all related concepts used in crystallography to describe the periodicity of a crystal lattice. While they may seem similar, they actually have distinct definitions and uses.

Q-spacing refers to the distance between two Bragg peaks in a diffraction pattern. This distance is measured along the direction of the incident X-rays and is used to calculate the spacing between planes of atoms in the crystal lattice.

Bragg-spacing, on the other hand, refers to the distance between two adjacent crystal planes in the lattice. This distance is measured in the actual crystal structure and is related to the Q-spacing by a mathematical equation.

D-spacing, also known as interplanar spacing, is the distance between two parallel crystal planes in the lattice. It is directly related to the Bragg-spacing and is used in diffraction experiments to determine the crystal structure of a material.

Repeat distance, sometimes called lattice spacing, is the distance between identical points on adjacent unit cells in a crystal lattice. It is related to the D-spacing and is used to describe the periodicity of the crystal lattice.

In summary, Q-spacing, Bragg-spacing, D-spacing, and repeat distance are all related to each other, but they have distinct definitions and uses in crystallography. Q-spacing is used in diffraction experiments, while Bragg-spacing, D-spacing, and repeat distance are used to describe the crystal lattice itself. Q refers to the scattering vector in diffraction experiments and is related to the other spacing parameters through mathematical equations.