Crystallographic Databases

Our objective is to provide critically evaluated, comprehensive crystal structure databases to enable materials identification required for the development of inorganic materials and devices. Our goal is to design, populate, and disseminate these NIST standard reference databases in forms that can be readily incorporated into commercial X-ray, neutron, and electron diffraction instruments.

NIST develops and provides crystal structure information in the form of three standard reference databases (SRD's): SRD 3 (NIST Crystal Data), SRD 83 (NIST Metals Structural Database), and SRD 84 (FIZ-NIST Inorganic Crystal Structure Database). SRD 3, although limited to crystallographic unit cell parameters and phase composition, is the most comprehensive in terms of materials classes, covering inorganic and organic materials, with about 250,000 entries. SRD 83 contains full crystallographic and atomic position information for about 60,000 metallic and intermetallic materials. SRD 84 contains full crystallographic and atomic position information for about 100,000 inorganic non-metallic materials. NIST continually develops scientific algorithms to evaluate crystal structure data, updates the three databases, and makes the databases available in a variety of formats.

Impact and Customers:

• Components and devices used in a broad spectrum of technology sectors such as health care, communications,energy, and electronics, are manufactured from crystalline inorganic materials. The development of advanced materials with new or improved properties for such components and devices requires accurate crystal structure data.

• NIST collaborates with Fachinformationszentrum Karlsruhe (FIZ), Germany, on the collection, formatting, evaluation, and distribution of crystal structure data in the form of the Inorganic Crystal Structure Database (ICSD), Standard Reference database (SRD) 84.

• Leading vendors of X-ray and electron diffraction measurement instrumentation and software distribute NIST crystal structure databases with measurement instruments or programs, typically as analysis options.

Development of advanced inorganic materials necessarily begins with the preparation and identification of the constituent chemical and crystallographic phases. Crystalline phases can be identified by their characteristic X-ray, neutron, and electron diffraction patterns by pattern-matching against crystal structure data already determined for phases known to form in a chemical system. SRD 3 and SRD 84 are continually updated by NIST researchers through critical evaluation of crystallographic data. In particular, collaboration between NIST and FIZ leads to the collection, critical evaluation, consistent formatting,and distribution of 2,000 to 10,000 new and revised inorganic non-metallic crystal structures per year, released twice-yearly as updates to SRD 84. The NIST Structural Database (NSD) is a comprehensive collection of crystal structures of ceramics 

Structure of Mg(Cu1-xAlx)2, a Friauf-Laves Phase, from the NSD

 

Phase Indentification by Electron Diffraction

and metals. This year, NIST achieved a long-awaited goal by releasing data on an additional 40,000 materials, bringing the total number of materials in the database to over 60,000. These NSD data were delivered to instrument manufacturers and software vendors for dissemination to the research community. The entire data set was evaluated with respect to measurement uncertainty, symmetry conventions,and data consistency. Upgrades to the data set include improved standardization of the data provided for each structure and additional data fields for each entry. Re-design of the database was undertaken with specific attention to the needs of instrument manufacturers who utilize the NSD as an analytical component of X-ray and electron diffraction instruments.

In collaboration with FIZ, NIST also produces the FIZ-NIST Inorganic Crystal Structure Database (ICSD), a comprehensive collection of data for inorganic crystalline materials. Although the original definition of the ICSD specifically excluded metals and intermetallic crystalline materials, with NIST's 2007 delivery of the NSD to collaborators in FIZ, the definition of the FIZ-NIST ICSD has been changed to cover all categories of non-organic materials, including inorganic and intermetallic compounds, metals, and minerals. The FIZ-NIST ICSD marks the beginning of a long-term plan to create and disseminate one comprehensive crystallographic database for all non-organic materials, to benefit researchers worldwide.