The NIST Chemistry WebBook provides users with easy access to chemical and physical property data for chemical species through the internet. The data provided in the site are from collections maintained by the NIST Standard Reference Data Program and outside contributors. Data in the WebBook system are organized by chemical species. The WebBook system allows users to search for chemical species by various means. Once the desired species has been identified, the system will display data for the species. Data include thermochemical properties of species and reactions, thermophysical properties of species, and optical, electronic and mass spectra.

FLYCHK provides a capability to generate atomic level populations and charge state distributions for low-Z to mid-Z elements under NLTE conditions.

The NIST Electron Inelastic-Mean-Free-Path Database provides values of electron inelastic mean free paths (IMFPs) principally for use in surface analysis by Auger-electron spectroscopy and X-ray photoelectron spectroscopy. The database includes IMFPs calculated from experimental optical data and IMFPs measured by elastic-peak electron spectroscopy. If no calculated or measured IMFPs are available for a material of interest, values can be estimated from the predictive IMFP formulae of Tanuma et al. and of Gries. IMFPs are available for electron energies between 50 eV and 10,000 eV although most of the available data are for energies less than 2,000 eV. A critical review of calculated and measured IMFPs has been published [C. J. Powell and A. Jablonski, J. Phys. Chem. Ref. Data 28, 19 (1999)].

This version of NIST Standard Reference Database 46 is a major enhancement to this widely used database which provides comprehensive coverage of interactions for aqueous systems of organic and inorganic ligands with protons and various metal ions and is based on the six-volume Critical Stability Constants by Martell and Smith. The new version contains 225 additional ligands, new data, data printing, rapid bibliography searching and more streamlined commands. New literature has resulted in revision and upgrading of 30% of previous data. Entire contents are critically selected for accuracy and consistency.

NIST X-ray Photoelectron Spectroscopy Database XPS contains over 33,000 data records that can be used for the identification of unknown lines, retrieval of data for selected elements (binding energy, Auger kinetic energy, chemical shift, and surface or interface core-level shift), retrieval of data for selected compounds (according to chemical name, selected groups of elements, or chemical classes), display of Wagner plots, and retrieval of data by scientific citation. For the newer data records, additional information is provided on the specimen material, the conditions of measurement, and the analysis of the data. Version 5.0 includes the addition of Digital Object Identifiers (DOI) to each of the citations. Additionally, Version 5.0 has new features including chemical shift plots, custom-built components for displaying both formatted molecular formulas and formatted spectral lines, and spectral sorting functions of photoelectron lines and Auger Parameters.

For over 40 years, NIST has provided well-documented numeric data to scientists and engineers for use in technical problem-solving, research, and development. These recommended values are based on data which have been extracted from the world''s literature, assessed for reliability, and then evaluated to select the preferred values. These data activities are conducted by scientists at NIST. NIST Data Gateway-provides easy access to many (currently over 80) of the NIST scientific and technical databases. These databases cover a broad range of substances and properties from many different scientific disciplines. The Gateway includes links to free online NIST data systems as well as to information on NIST PC databases available for purchase.

The NDRL/NIST Solution Kinetics Database contains data on rate constants for solution-phase chemical reactions. The database is designed to be searched by reactants, products, solvents, or any combination of these. In addition, the bibliography may be searched by author name, title words, journal, page(s), and/or year. This is not the same database as the one at Notre Dame, although both databases share a common data source.

The HIV Protease Structural Database is an archive of experimentally determined 3-D structures of Human Immunodeficiency Virus 1 (HIV-1), Human Immunodeficiency Virus 2 (HIV-2) and Simian Immunodeficiency Virus (SIV) Proteases and their complexes with inhibitors or products of substrate cleavage.

This database is the product of a multi-year, comprehensive evaluation and expansion of the world's most widely used mass spectral reference library.

description: This database provides reference data on controlled cell image experiments. The database contains cell images of A-10 rat smooth muscle and NIH-3T3 mouse fibroblasts. A novel rule and root based method is used to create experimental metadata as described in About Us page.; abstract: This database provides reference data on controlled cell image experiments. The database contains cell images of A-10 rat smooth muscle and NIH-3T3 mouse fibroblasts. A novel rule and root based method is used to create experimental metadata as described in About Us page.

description: The Elemental Data Index provides access to the holdings of NIST Physical Measurement Laboratory (PML) online data organized by element. It is intended to simplify the process of retrieving online scientific data for a specific element from various online databases, including atomic spectroscopy, atomic data, x-ray absorption, and nuclear data. For some of the databases, the data are immediately retrieved; for others, the retrieval form is provided with the element entered in the form, but additional options must be selected in order to retrieve the data. Each of the databases can be individually accessed from the PML's Physical Reference Data page (http://pml.nist.gov/data).; abstract: The Elemental Data Index provides access to the holdings of NIST Physical Measurement Laboratory (PML) online data organized by element. It is intended to simplify the process of retrieving online scientific data for a specific element from various online databases, including atomic spectroscopy, atomic data, x-ray absorption, and nuclear data. For some of the databases, the data are immediately retrieved; for others, the retrieval form is provided with the element entered in the form, but additional options must be selected in order to retrieve the data. Each of the databases can be individually accessed from the PML's Physical Reference Data page (http://pml.nist.gov/data).

A web database is provided which can be used to calculate photon cross sections for scattering, photoelectric absorption and pair production, as well as total attenuation coefficients, for any element, compound or mixture (Z <= 100) at energies from 1 keV to 100 GeV. XCOM provides two forms of output: (a) tables which correspond closely in format to existing tables in the literature; (b) graphical display of the tabular data. Access to the database is provided through a web-based form located at: http://physics.nist.gov/PhysRefData/Xcom/html/xcom1.html.

description: This X-ray transition table provides the energies and wavelengths for the K and L transitions connecting energy levels having principal quantum numbers n = 1, 2, 3, and 4. The elements covered include Z = 10, neon to Z = 100, fermium. There are two unique features of this database: (1) all experimental values are on a scale consistent with the International System of measurement (the SI) and the numerical values are determined using constants from the Recommended Values of the Fundamental Physical Constants: 1998 [115] and (2) accurate theoretical estimates are included for all transitions. Version 1.2; abstract: This X-ray transition table provides the energies and wavelengths for the K and L transitions connecting energy levels having principal quantum numbers n = 1, 2, 3, and 4. The elements covered include Z = 10, neon to Z = 100, fermium. There are two unique features of this database: (1) all experimental values are on a scale consistent with the International System of measurement (the SI) and the numerical values are determined using constants from the Recommended Values of the Fundamental Physical Constants: 1998 [115] and (2) accurate theoretical estimates are included for all transitions. Version 1.2

description: The Inorganic Crystal Structure Database (ICSD) is produced cooperatively by the Fachinformationszentrum Karlsruhe (FIZ) and the National Institute of Standards and Technology (NIST). Components and devices used in a broad spectrum of technology sectors such as health care, communications, energy and electronics are manufactured from crystalline materials; the development of advanced crystalline materials requires accurate crystal-structure data. SRD 84 ICSD provides critically evaluated, comprehensive crystal-structure data and search software that enable phase identification by their characteristic diffraction patterns using X-rays, neutrons and electrons. SRD 84 ICSD contains full crystallographic and atomic-position information for more than 180,000 non-organic materials, including inorganics, ceramics, minerals, pure elements, metals and intermetallics, published in literature from 1913 through the present. ICSD is updated twice a year, with each update comprising about 2,000 to 10,000 new or re-evaluated entries. Data items include bibliographic information, compound designation such as chemical name, chemical formula, mineral name; and crystallographic parameters such as unit cell, space group, element symbol with numbering, oxidation state, multiplicity for Wyckoff position, x,y,z coordinates, site occupation, thermal parameters and reliability index R, among others. A free demonstration CD which includes a comprehensive user interface, FindIt, for a demo database is available upon request or can be downloaded from the website https://www.nist.gov/srd/nist-standard-reference-database-84.; abstract: The Inorganic Crystal Structure Database (ICSD) is produced cooperatively by the Fachinformationszentrum Karlsruhe (FIZ) and the National Institute of Standards and Technology (NIST). Components and devices used in a broad spectrum of technology sectors such as health care, communications, energy and electronics are manufactured from crystalline materials; the development of advanced crystalline materials requires accurate crystal-structure data. SRD 84 ICSD provides critically evaluated, comprehensive crystal-structure data and search software that enable phase identification by their characteristic diffraction patterns using X-rays, neutrons and electrons. SRD 84 ICSD contains full crystallographic and atomic-position information for more than 180,000 non-organic materials, including inorganics, ceramics, minerals, pure elements, metals and intermetallics, published in literature from 1913 through the present. ICSD is updated twice a year, with each update comprising about 2,000 to 10,000 new or re-evaluated entries. Data items include bibliographic information, compound designation such as chemical name, chemical formula, mineral name; and crystallographic parameters such as unit cell, space group, element symbol with numbering, oxidation state, multiplicity for Wyckoff position, x,y,z coordinates, site occupation, thermal parameters and reliability index R, among others. A free demonstration CD which includes a comprehensive user interface, FindIt, for a demo database is available upon request or can be downloaded from the website https://www.nist.gov/srd/nist-standard-reference-database-84.

The IUPAC Solubility Data Series Volumes 1-103 (1979 to 2014) are made available online. Volumes 1-19 and 39-65 are available as scanned and OCR'd single PDF files. Volumes 20-38 are available with each volume indexed and sectioned into multiple PDF files that can browsed using an online table of contents. Volumes 66-103 are available through links to the document at the Journal of Physical and Chemical Reference Data. The electronic part of the database contains 67,500 solubility measurements, compiled from 18 volumes of the IUPAC Solubility Data Series. There are about 1800 chemical substances in the database and 5200 systems, of which 473 have been critically evaluated. The database has over 1800 references.

This database provides access and search capability for NIST critically evaluated data on atomic energy levels, wavelengths, and transition probabilities that are reasonably up-to-date. The Atomic Spectroscopy Data Center has carried out these critical compilations. The Data Center is located in the Physical Measurement Laboratory at theNational Institute of Standards and Technology (NIST).

This is a database of total ionization cross sections of atoms and molecules by electron impact. The cross sections were calculated using the Binary-Encounter-Bethe (BEB) model, which combines the Mott cross section with the high-incident energy behavior of the Bethe cross section. Selected experimental data are included. Singly differential cross sections are included for H, He, and H2. Electron-impact excitation cross sections are also included for selected atoms.

This site, developed in the Physics Laboratory at NIST, addresses three topics: fundamental physical constants, the International System of Units (SI), which is the modern metric system, and expressing the uncertainty of measurement results.

The data that formerly appeared here have been superseded by the data that now appear at the Decay Data Evaluation Project http://www.lnhb.fr/nuclear-data/nuclear-data-table/.

This database contains the rotational spectral lines observed and reported in the open literature for 91 hydrocarbon molecules through September 1987. The isotopic molecular species, assigned quantum numbers, observed frequency, estimated measurement uncertainty and reference are given for each transition reported. In addition to correcting a number of misprints and errors in the literature cited, the spectral lines for many normal isotopic species have been refit to produce a comprehensive and consistent analysis of all the data extracted from various literature sources. The derived molecular properties, such as rotational and centrifugal distortion constants, hyperfine structure constants, electric dipole moments, and rotational g-factors are listed.