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.

Chemical Block Layered Alignment of Substructure or Chem-BLAST uses a method for finding chemical compounds within a large collection. In this method, all chemical compounds are annotated in terms of standard chemical structural fragments. These fragments are then organized into a data tree based on their chemical substructures. Search engines have been developed to use this data tree. These search engines use the Chem-BLAST technique to search on the fragments and look for their chemical structural neighbors.

This repository provides a source for interatomic potentials (force fields), related files, and evaluation tools to help researchers obtain interatomic models and judge their quality and applicability. Users are encouraged to download and use interatomic potentials, with proper acknowledgement, and developers are welcome to contribute potentials for inclusion. The files provided have been submitted or vetted by their developers and appropriate references are provided. All classes of potentials (e.g., MEAM, ADP, COMB, Reax, EAM, etc.) and materials are welcome.

The Web Thermo Tables (WTT) are a collection of critically evaluated thermodynamic property data for pure compounds with a primary focus on organics. These data were generated through dynamic data analysis, as implemented in the NIST ThermoData Engine software package. Also included are some critically evaluated data from the historical TRC Thermodynamic Tables archive. The Professional Edition contains information on over 28,000 compounds.

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.

**** Note that this SRD is superseded by SRD 64 Version 4.0. ****The NIST Electron Elastic-Scattering Cross-Section Database provides values of differential elastic-scattering cross sections, total elastic-scattering cross sections, phase shifts, and transport cross sections in electron-atom scattering for elements with atomic numbers from 1 to 96 and for electron energies between 50 eV and 300 keV (in steps of 1 eV).

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.

The NIST Electron Effective Attenuation Length Database provides values of electron effective attenuation lengths (EALs) in materials at user-selected electron energies between 50 eV and 2,000 eV. The database was designed mainly to provide EALs (to account for effects of elastic-electron scattering) for measurements of the thicknesses of overlayer films and, to a much lesser extent, for measurements of the depths of thin marker layers. EALs are calculated using an algorithm based on electron transport theory for measurement conditions specified by the user.

The NIST Database for the Simulation of Electron Spectra for Surface Analysis (SESSA) can be used to simulate Auger-electron spectra and X-ray photoelectron spectra of nanostructures such as islands, lines, spheres, and layered spheres on surfaces. As for earlier versions, such simulations can be performed for multilayer films. Users can specify the compositions and dimensions of each material in the sample structure as well as the measurement configuration. The database contains extensive physical data needed for quantitative interpretations of observed spectra.

This database provides values of backscattering correction factors (BCF) of homogeneous materials for quantitative surface analyses by Auger electron spectroscopy. These BCFs are obtained from Monte Carlo simulations based on two models of electron transport in the material, a simplified model and an advanced model [A. Jablonski and C. J. Powell, Surf. Science 604, 1928 (2010)]. One assumption for the former model is that the primary-electron beam is unchanged, in intensity, energy or direction, within the information depth for Auger-electron emission.