Ten Years Later
The ten year license for our PDF-2 Release 2006 databases are expiring within the next year. Below you will find a review of ICDD’s product growth and development since 2006. The figures offer a comparison of 2006 data vs. 2016 data that displays the impact of our PDF-2 and PDF-4 development over the last decade.
Powder Diffraction File™ (PDF®) databases are designed for phase identification. Comprehensive coverage is obtained by combining data from single crystal and powder diffraction experiments. ICDD has three database sources that provide large continuous annual updates, ICSD—Fachinformationszentrum Karlsruhe (FIZ), MPDS—Materials Phases Data System, and ICDD―International Centre for Diffraction Data. The NIST—National Institute of Standards and Technology database is a fixed compilation, while the ICDD Crystal Data (05) is a new database. As shown in the comparison above, all major databases significantly increased in content in the last 10 years. Both ICSD and MPDS contributions grew rapidly because of annual additions and historical data reviews. The ICSD and NIST contributions to the PDF-4+ database are smaller than in PDF-2 because ICDD reviews and eliminates duplicate data and the remaining data are unique. Because of this process, PDF-4+ products always have the most comprehensive coverage because it uses more sources of data and has more unique data. In phase identification PDF-4+ outperforms any other database, freeware or commercial, because of this comprehensive coverage.
PDF-4+ has more: More data, more sources of data, and more contributing authors.
PDF-4 databases differ from the PDF-2 database in the ability to perform quantitative analyses. There are several well-known pattern fitting methods that can be used for quantitative analysis. The Rietveld method requires atomic coordinates. The LeBail method requires an indexed pattern and the Reference Intensity Ratio (RIR) method requires a scale factor (I/Ic) standardized to corundum.
In the past 10 years, the ICDD has added more data from more sources, including atomic coordinates. The completion of historical reviews have added large numbers of atomic structures and the PDF-4+ product has the biggest and chemically most diverse compilation of atomic structures for inorganic materials in the world.
Another unique feature of the PDF-4+ database is the inclusion of full digital experimental patterns. These patterns are particularly important for analyzing noncrystalline materials (clays, polymers, and pharmaceuticals), nanomaterials, and crystallinity. Most of these experimental patterns are sourced from the ICDD and are unique to the PDF-4 databases.
All materials are not equal. Some like quartz or iron are found in enormous natural abundance in locations all around the world, while others are man-made, analyzed once, and never seen again. ICDD targets additions of abundant natural materials (i.e. minerals, metals) and man-made materials of commercial significance. This is because these are the materials most likely to be found in the world’s analytical, law enforcement, and materials analysis laboratories; independent of whether the laboratory is commercial, government or academic. Targeting is performed by targeted literature searches, editorial data extraction, and through grants to various research institutes. All data are then reviewed by field experts, including ICDD editors and volunteer members. The end result is ICDD’s unique subfile system that categorizes and classifies materials based on chemistry and/or application. The purpose of this system is simple. It guides any user to target the appropriate chemistry or application, dramatically improving the accuracy of your analysis.
These are some of the most common subfiles used in inorganic material analysis. The large increases in mineral content during the last decade are a direct result of the targeting process and the hard work of mineralogists in reviewing and classifying all of the world sources of mineral data. Today, ICDD’s mineral subfile in PDF-4+ has 97% of all named mineral species, hundreds of unnamed minerals and a massive collection (tens of thousands) of mineral polytypes. An example of the latter would be the different hydration states, and anion and cation substitutions in montmorillonite clay. This allows any analyst, anywhere in the world, to identify the minerals in their backyard. It is also being used by the Mars Science Laboratory to study the minerals on Mars. Similar growth can be seen in the other subfiles, as shown above, that are the product of dedicated editorial teams.
Release 2006 of the Powder Diffraction File went from 21 subfiles + 13 subclasses to 31 subfiles + 19 subclasses in Release 2016. This growth was promoted by ICDD member scientists, the majority of whom work in materials analysis. New materials are constantly being developed and the ICDD and its membership update the subfile classifications to keep relevant.
Some of the largest changes in materials in the past decade have come from the growth of the computer industry and research into alternative energy sources.
This has resulted in some new subfiles, such as thermoelectric materials, hydrogen storage materials, and battery materials, as well as significant growth in other subfiles such as semiconductors and ferroelectrics. To keep pace with new developments in the materials community, ICDD continuously monitors these subfiles and adds new materials to the Powder Diffraction File each year.
ICDD also edits, produces, and distributes the PDF-4/Minerals and PDF-4/Organics databases. PDF-4/Minerals contains the mineral subfile and is a subset of PDF-4+. It is typically used by mining operations and geology departments. PDF-4/Organics has all the attributes described above, but with a different focus on targeted materials.
PDF-4/Organics has the world’s most comprehensive collections of pharmaceuticals, pigments, polymers, and excipients. This arises from the combination of single crystal historic data from the Cambridge Structural Database (CSD -2010 and earlier), powder diffraction data from the ICDD, and modern single crystal data extracted by the ICDD. The CSD contains the largest collection of organic crystallographic data, while PDF-4/Organics contains the largest collection of commercial organic materials. The latter includes many materials from ICDD grants that are sole sourced to the PDF databases. Because of the targeted content, PDF-4/Organics outperforms all other freeware and commercial databases in pharmaceutical and forensic materials analysis.