ICDD’s Mission
To be the world center for quality diffraction data, meeting the needs of the technical community.

To promote the application of materials characterization methods in science and technology, by providing a forum for the exchange of ideas and information and through publication of X-ray diffraction data.

The PDF Databases
Release 2009 of the Powder Diffraction File contains 628,155 unique material data sets. Each data set contains diffraction, crystallographic and bibliographic data, as well as experimental, instrument and sampling conditions, and select physical properties in a common standardized format. The PDF’s large size and comprehensive material coverage is achieved through ICDD’s historical sources of powder diffraction data, ICDD’s Grant-in-Aid Program, contributions, and bibliographic searches, as well as collaborations with international crystallographic database organizations.

The database is designed and produced in several different formats in order to serve different groups of users.

PDF-2 is a collaborative product between ICDD, FIZ and NIST and is designed for inorganic materials analyses. Many common organic materials from ICDD are added to this database to facilitate rapid material identification. (purchase)

PDF-4+ is an advanced database containing the data from both the PDF-2 and ICDD’s collaboration with MPDS. This database has comprehensive material coverage for inorganic materials and it contains numerous features such as digitized patterns, molecular graphics and atomic parameters. Many new features have been incorporated into PDF-4+ to enhance the ability to do quantitative analysis by any of three methods: Rietveld Analysis, Reference Intensity Ratio (RIR) method or Total Pattern Analysis. PDF-4+ is available on CD, DVD, or accessed via the Internet using WebPDF-4+ with a USB compatible dongle. (purchase)

PDF-4/Minerals is a subset of PDF-4+, which includes the new features incorporated into PDF-4+. (purchase)

PDF-4/Organics is a collaborative product between ICDD and CCDC. It is designed to identify organic and organometallic materials and also contains a few thousand inorganic materials, primarily pharmaceutical excipients to help with formulation analyses and identification. (purchase)

Printed Books and Indexes include ICDD’s experimentally collected diffraction patterns and search manuals. These materials have been produced annually for 59 years and are commonly used as reference books. (purchase)

Compare PDF-4+ 2009 using DDView+ with PDF-2 Release 2009 using DDView

The PDF Databases

Value

This catalog marks the fifth consecutive year that ICDD has not changed database prices. During this timeframe, the PDF databases have dramatically increased in size and technical capability. Table 1, shown below, outlines the increases in entries, searches and display fields for the last five annual product releases. This demonstrates ICDD’s commitment and dedication, as a nonprofit organization, to bring the highest value to the scientific community. Enhanced capabilities were achieved by using a flexible database housing (Sybase®) combined with JAVA™ “point and click” interfaces in our associated software. This has enabled rapid growth in both search and display options, which can be selected, sorted, combined and displayed in nearly limitless combinations. This data mining capability has been interfaced to a versatile graphic display and plotting program. Examples of output from these programs are shown throughout this website.

 

More data, Higher quality

For Release 2009, PDF users can expect more data and more quality in all PDF databases. ICDD continues to collect data from global sources, including collaborating database organizations. In recent years, ICDD has been processing over 50,000 entries per year and publishing a slightly smaller number that pass through the ICDD quality checking system and duplicate removal processes. All ICDD entries can be traced to a unique reference, typically a scientific publication, but also to contributions, grants and patents. General characteristics for each database are described below.

The ICDD editorial process utilizes a combination of full-time scientific editors, volunteer member field experts, and contracted subject matter experts to review and categorize the data. Prior to editorial review, new and old data are annually reviewed by a suite of proprietary editorial programs that go through over 100 quality checks, which flag inconsistencies and discrepancies for the editors. The programs also analyze similar entries through bibliographic, property, diffraction and crystallographic data to eliminate duplicates and assign cross-references.

This quality system identifies and removes most errors before they are published in the Powder Diffraction File. If errors are not resolved or if insufficient information is available from the reference, then the entry may be deleted or assigned a lower quality mark. The comment section of the entry will tell the user the exact reason why the quality was lowered. In 2009, the total number of “lowered” quality comments in PDF-2 and PDF-4+ were actually decreased because of recent editorial process updates, both by ICDD and ICDD’s database partners, that corrected thousands of entries.

Quality has also changed with time. This is attributed to improvements in analytical instrumentation and analysis software. There is more frequent usage of certified standards, both for instrument calibration and reference analyses. In addition, there are now extensive data checking and editing programs that analyze and remove many errors prior to publication, both for journal publication and publication as a reference in the Powder Dif fraction File. The statistics of quality improvements is demonstrated in Figures 2 and 3 for PDF-4+ and PDF-4/Organics databases.

Improved Phase Identification

The quality improvements shown above have a direct impact on phase identification processes. Independent of whether phase identification is performed by classic d,I pair analysis or by total pattern comparisons, the accuracy of the reference in comparison to an unknown is improved with higher quality reference data. All commercial search/match programs demonstrate improved multiphase identification when both high quality experimental data and reference data are compared. Programs that use residual analysis have a more accurate residual pattern when the reference patterns are more accurate. This results in higher goodness of merit values (or numbers), less false positives and an improved ability to analyze minor and trace phases. As shown in the above two figures, there are significant amounts of new high quality reference data being added to the PDF databases each year.

The phase identification process is also facilitated by combining data sources from around the world. An excellent example is shown for PDF-4/ Minerals where there are >10,000 mineral entries from three of our collaborative database partners (see above). This allows the best quality data to be selected by your search/match programs from a diversity of mineral types from around the world. As shown in Table 1 (below), the available mineral content has doubled in the last 5 years by combining international sources of data and having an ICDD task team of mineralogists work on identifying and classifying mineral content from these sources.

Subfiles

Over a period of several years, ICDD has applied the field expertise of its members for the selection and editorial evaluation of subfiles. Originally, subfile designations were just applied to the experimental powder diffraction data, but starting in 2003 this system was applied to all database contributions and sources to the Powder Diffraction File. From 2005–2007, this system was automated resulting in dramatic content increases in all subfiles. Today, all new data are analyzed automatically for subfile content, followed by editorial review by field experts. This system is unique to the Powder Diffraction File databases in both its depth and breadth of analysis.

Subfiles help all users by targeting the analysis and eliminating false positives. As databases grow to hundreds of thousands of materials and tens of millions of d-spacings, the use of subfiles becomes an increasingly more important tool. The subfile system improves any search process and nearly all ICDD software distributors take advantage of ICDD’s subfile systems. Look for this option with your vendor software.

ICDD web site: www.icdd.com/resources/tutorials/