ICDD PDF-4
Definition
The Powder Diffraction File maintained by the International Centre for Diffraction Data. A reference database of more than 400,000 crystalline phases that XRD software searches against to identify an unknown pattern. The forensic equivalent of looking up a fingerprint in a national database.
- Full name
- Powder Diffraction File, release 4
- Maintainer
- International Centre for Diffraction Data
- Size
- Over 400,000 crystalline phase entries
- Used with
- XRD pattern-matching software
Common questions
What happens when an unknown XRD pattern does not match any PDF-4 entry?+
The analyst reports the closest partial matches and unindexed peaks rather than a positive identification, and may turn to complementary techniques such as XRF or Raman spectroscopy to narrow the composition further.
Is a PDF-4 database match alone sufficient for a court identification?+
A strong pattern match is strong supporting evidence, but the examiner still evaluates peak quality, sample purity, and mixture effects, since real crime-scene samples are rarely pure single-phase crystals.
Related terms
- Bragg's Law
- nλ = 2d sin(θ). A monochromatic X-ray beam diffracted off the parallel lattice planes of a crystal produces constructive interference only at...
- Characteristic X-Ray
- An X-ray photon emitted when an outer-shell electron drops into an inner-shell vacancy created by ionisation. Energy is set by the difference...
- EDXRF vs WDXRF
- Energy-dispersive XRF reads all photon energies in parallel with a Si(Li) or silicon-drift detector; fast, cheap, lower resolution. Wavelength-dispersive XRF uses a...
- GSR Pb-Sb-Ba Signature
- The classical elemental signature of inorganic gunshot residue: lead from the bullet core, antimony from the priming compound, barium from the priming...
- Moseley's Law
- The square root of the characteristic X-ray frequency varies linearly with atomic number Z. Discovered by Henry Moseley in 1913, it is...