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Powder Diffraction File: Definitions

Note: This guide is no longer updated.

Significant Figures

Significant figures vary throughout the database. In the early years, two significant figures beyond the decimal point were usually the best that could be obtained. Currently, up to seven may be supplied.

Data Quality Marks

Quality Marks (QM) are assigned based upon a number of parameters (see the Help document in the PDF software).

QM Term Definition
S or ★ Star

high-quality diffractometer or Guinier data, chemical composition has been well-characterized, intensities have been measured objectively, good range and even spread of intensity, etc.

R Rietveld d-values are directly the result of Rietveld refinement of the data (only accepted in unusual cases)
G Good material has significant amorphous content and has a digital diffraction pattern with good signal-to-noise ratio
I Indexed pattern has been indexed; therefore, the material is almost certainly single-phase
C Calculated calculated from single-crystal structural parameters; structural refinement R-factor was <0.10
P Prototyping used in the LPF. Prototype structure is an editorial action (i.e., assigned by the PDF editor, not the original source) to assign space group coordinates for entries that have not determined this from the primary literature
M Minimal Acceptable similar to good except no chemical analysis data was submitted to support the materials composition 
B Blank does not meet Star, Indexed, or Low-Precision criteria
O Low-Precision data taken on poorly characterized material or data known (or suspected) to be low precision
H Hypothetical calculated from the atomic positions and thermal parameters of an isostructural compound

Data Sources

The original data was experimentally derived. As other sources of data were added to the database, prefix numbers were assigned to the source. Specific subsets of the database can be searched separately and results sets can be sorted by source. This is useful when the compound is a known type (mineral, organic) or a data-gathering method is prefrered (experimental, calculated).


Source Source Prefix Set Card Old 6-Digit Card New 9-Digit Card
Experimental (ICDD) 00 yyy xxxx 56-2000 00-056-2000
ICSD (FIZ) 01 yyy xxxx 70-4508 01-070-4508
CSD (CCDC) 02 yyy xxxx 72-2828 02-072-2828
NIST 03 yyy xxxx 65-8423 03-065-8423
LPF 04 yyy xxxx NA 04-001-0001


Source definitions:

Abbreviation Full Name Data Type
ICDD International Centre for Diffraction Data mix
ICSD (FIZ) FIZ (Fachinformationszentrum) Karlsruhe mix
CSD (CCDC) Cambridge Crystallographic Data Centre organic
NIST National Institute of Science and Technology inorganic
LPF (MPDS) Linus Pauling File inorganic