X-Ray Diffraction

Definition

Powder X-ray Diffraction (XRD) is one of the primary techniques used by mineralogists and solid state chemists to examine the physico-chemical make-up of unknown solids. This data is represented in a collection of single-phase X-ray powder diffraction patterns for the three most intense D values in the form of tables of interplanar spacings (D), relative intensities (I/I_o), and mineral name.

The XRD technique takes a sample of the material and places a powdered sample in a holder, then the sample is illuminated with x-rays of a fixed wave-length and the intensity of the reflected radiation is recorded using a goniometer. This data is then analyzed for the reflection angle to calculate the inter-atomic spacing (D value in Angstrom units - 10^-8 cm). The intensity(I) is measured to discriminate (using I ratios) the various D spacings and the results are to identify possible matches.

Search X-Ray Diffraction Table

Users can now search on D₁, D₂, D₃, and chemical formula in any order from the Table of X-Ray spacing. The search is based on reported values from each mineral where a diffraction file has been published. Two theta values can be calculated for different wavelengths based on commonly used X-Ray anode values. In addition, the user can input any value for X-Ray wavelength and the 2 theta angles are calculated for that wavelength.

Optional Search Query - To Reset, Click Here

Some important observations:

1. Minmax tolerance is % so that all D values with a +/- range in percent are returned. The default is 10%.
2. The wild card character for formula searches is "%" and is required, the search is case sensitive, and the order is important. For example, %K%Na% will give different results than %Na%K% depending on the order the element occurs in the formula.
3. You can use any combination of D1, D2, D3 and formula.
4. Try increasing the tolerance. The larger the tolerance, the more records are found.
5. Don't get too involved with complicated formula searches, one or two elements work best. Don't forget the % wild card in the search.

Other References to X-Ray Diffraction

Search the Mineralogy Database

Example Subject Searches

Example: intensity-o1.76* finds all minerals with the most intense d-spacing of 1.76 to 1.7699 angstroms
Example: "intensity-o-2.5*" "2.9*" "3.99*" finds all minerals that have d-spacings starting at 2.5 to 2.5999 angstroms with data at 2.9 to 2.999 and 3.99 to 3.999 angstroms, index of refraction, % element, etc.

Search the Web

X-Ray Analysis of a Solid

Internet course at Birkbeck College

Table of X-Ray Diffraction Values In the Mineralogy Database