 |
A Powder Diffraction File |
Course Material Index
Section Index
Previous Page
Next Page
A Powder Diffraction File
Although cards are no longer a purchasable medium for the Powder Diffraction
File, they still present a useful visual display of the type of information
contained within the PDF database. In the images below we show two typical card
entries, the first displaying a full range of information, the latter showing
the bare minimum:
 (151 kBytes) |
 (144 kBytes) |
Taking the first case, we can find the following sets of information on the
card:
- an address for the entry ("7-216");
- a 4 × 2 table
containing d spacings
and observed I/I1 values for the three
strongest diffraction peaks;
- a box containing the chemical formula,
chemical name, and mineral or common name;
- a box of essential parameters describing
how the powder pattern was collected;
- a box containing the crystallographic parameters
for the material;
- a box containing basic physical parameters
for the material;
- a comment box;
- a table consisting of three columns
(d spacings; I/I1 values; hkl
indices).
The intensities of the peaks in the powder pattern are normalised with respect
to the intensity of the strongest peak, which has relative intensity 1.0
(= 100%) and is labelled I1.
The observed intensities of the other peaks are therefore listed as
I/I1 values.
In the second case, much of the above information is missing. In principle the
barest workable minimum would be:
- the address;
- a 4 × 2 table containing d
and observed I/I1 values for the three
strongest diffraction peaks;
- the box with at least some identifying name for the material;
- the table with at least the first two columns
(d values; I/I1 values).
The crystallographic and other information are extremely useful but not vital
for identification purposes. Indeed the crystal structure of the material need
not even be known for identification purposes and crystallographic parameters
and hkl indices will not be found in every case.
Course Material Index
Section Index
Previous Page
Next Page