We are returning to the topics of inorganic and structural databases at the Struktura conferences quite often. The first extended abstract appeared in 2007 [1] and then in 2015 [2]. The current one is just update of [2].
Powder Diffraction File - PDF
The database is developed, edited and maintained by the ICDD - the International Centre for Diffraction Data [3]. Table 1 an updated version of table from [2]. The development can be seen.
Table 1. PDF versions available
|
Version |
Brief characterization |
Entries in 2014 |
Entries in 2018 |
|
PDF-4+ |
Comprehensive collection of data for inorganic materials, produced in a standardized format that can be rapidly searched for unknown phase identification. Extensive data mining is facilitated with 125 display fields coupled with 72 searches. |
354 264 |
398 726 |
|
PDF-2 |
Uses older format with less data but it is licensed for 5 year |
274 443 |
298 258 |
|
PDF-4+/Organics |
is a comprehensive database for phase identification combining both single crystal and powder diffraction data for organics and organometallics |
494 966 |
526 126 |
|
PDF-4+/Minerals |
Ninety-seven percent of all known mineral types, as defined by the International Mineralogical Association (IMA), are represented in the database, as well as many unclassified minerals. |
41 423 |
45 497 |
Single license of the first four versions for one year is 8 860 USD (5 875 USD for Academics), one-year renewal for 1 960 USD (1 250 USD). See icdd.com for 3-year, 5-year or site licenses.
Traditional form of the database is PDF-2 and it is a collaborative product between ICDD, FIZ (Karlsruhe) and NIST (National Institute of Standards). Each record contains table of interplanar spacings (d), relative intensities (I) and often also diffraction indices (hkl). In addition, chemical formula, chemical name, mineral name for minerals, crystal system, some physical characteristics, experimental parameters, bibliographic information and mark of data quality. This variant of the database is well-suited for phase analysis either with the Sieve software included free or with any commercial software for phase analysis when the user does not need necessarily advanced features of PDF-4+. Licensing is also more convenient.
In the last decade, the official variant is PDF-4+. database has comprehensive material coverage for inorganic materials and it contains numerous additional features such as digitized patterns, molecular graphics, and atomic coordinates. Data simulation programs enables the analysis of X-ray, neutron, electron, and synchrotron data
The database has the following features (2018)
• All entries have calculated digital
patterns
• 300 078 entries have I/Ic values for quantitative analysis by
Reference Intensity Ratio (RIR)
• 295 309 entries with atomic coordinates for quantitative analysis by the
Rietveld method
The PDF-4 license is strictly limited to a single computer (for single license) and time limited. If expired, nothing works.
WebPDF-4+ + is delivered as a USB compatible dongle. It provides portability for accessing the PDF-4+ database via the internet and enables full functionality of the PDF-4+ database using a high-speed internet connection.
PDF-4/Organics is a database with the largest collection of pharmaceutical excipients and polymer materials. It is designed for a multitude of applications in pharmaceutical, regulatory, specialty chemical, biomaterial, and forensic fields. The product has all of the display software and data mining capabilities contained in the PDF-4 family of products.
More can be found at http://www.icdd.com/
In this year presentation, we will focus on direct phase analysis with PDF-4
and specific applications. SIeve for PDF-2 and SIeve+ for PDF-4,
are integrated into the ICDD databases to allow phase analysis based in
different indexes. SIeve+ features automatic rotation of the eight strongest
lines (Hanawalt) or the eight longest of the strongest lines (Fink) or the
eight longest lines (Long8) to look for entries that exhibit the best Goodness
of Match (GOM). It allows also identification of some non-crystalline materials.
The Sieve is free for PDF-2 and Sieve+ is free for trial for 30 days. Since the
fundamental algorithms used by SIeve/SIeve+ are different than those used by
most commercial software programs, they can be strongly complementary.
Many useful presentations on the use of PDF can be downloaded from http://www.icdd.com/resources/tutorials/index.htm. Some of them will be used during the presentation.
The menu on the above page is divided into several items.
Materials
For example, how to analyze minerals, drugs, polymers, how to construct Pearson
symbol codes
Analysis Capabilities
Crystallite size analysis with PDF-4, trace phase analysis,
non-stoichiometric oxides, solid solutions, quantitative phase analysis, using
similarity indexes
PDF-4+
pattern simulations, 2D patterns, molecular graphics, 3D structure graphics
PDF-4 Organics
polymorph analysis, organic results, pharmaceuticals
XRF, Electron diffraction, Neutron diffraction, synchrotron
A few presentations on these techniques
Open structural and related databases
A list of primary and secondary crystallographic databases can be found at https://www.iucr.org/resources/data.
COD – Crystallography Open Database [3] that is - Open-access collection of crystal structures of organic, inorganic, metal-organic compounds and minerals, excluding biopolymers [4] has become quite popular since nowadays there are 394 978 entries there. The search interface is very simple including basically text, up to 8 elements chemical search (Boolean logics), cell volume limits, journal, year, volume, issue, Z-limits, lattice parameters limits. However, then CIF files are available containing all necessary structural information as well as JSmol structure preview. The database can be used in commercial software for phase analysis like the software of X-ray equipment vendors (as Panalytical, Bruker, Rigaku) or cheaper software like Match from Crystal Impact (http://www.crystalimpact.com/).
Open mineralogical databases and very user-friendly quite comprehensive Pearson’s Crystal Data – PCD (also from Crystal Impact) have been mentioned in [2]. The PCD currently contains about 304,000 structural data sets (including atom coordinates and displacement parameters, when determined) for about 173,000 different chemical formulas, roughly 18,500 experimental powder diffraction patterns and about 284,000 calculated patterns (interplanar spacings, intensities, Miller indices). In addition, over 42,500 figure descriptions for such as cell parameters as a function of temperature, pressure or concentration are given. To reach this result, scientific editors have critically analyzed and processed over 98,400 original publications (http://www.crystalimpact.com/).