Reading and sources

Where to read more, and where every number on this site comes from. Nothing here is a calculator — it is the shelf behind them.

Start here

One book, if you are going to read one. It assumes no crystallography and gets as far as space groups and diffraction without ever asking you to take a symmetry argument on trust, which is rarer than it sounds.

Introduction to Crystallography: Frank Hoffmann, Springer, 2020; Symmetry from the ground up: point groups, the 230 space groups, how to read an International Tables page, and what a diffraction pattern is telling you. It is the book to read alongside the space group tables here.
Faszination Kristalle und Symmetrie: Frank Hoffmann, Springer Spektrum, 2016; The German original of the same book, under a different title.

The tables this site computes from

These are the published sources the calculators are built on. Where a dataset is shipped with the site it was generated from the source below by a script in the repository, never transcribed by hand.

International Tables for Crystallography: International Union of Crystallography; The reference work. Volume A is the 230 space groups — their symmetry operations, general and special positions, and reflection conditions; Volume C carries the atomic scattering factors behind the structure factor.
spglib: Atsushi Togo and contributors; A crystal symmetry library whose database encodes the symmetry operations of all 530 settings the Tables list. It is the machine-readable route to Volume A used here: the operations are read from it, and everything this site says about a space group — the conditions, the elements, the general position — is derived from those operations rather than transcribed.
Atomic weights and isotopic compositions: NIST, Physical Measurement Laboratory; The isotope masses and representative abundances behind the isotope pattern. Every mass on this site that is not a standard atomic weight comes from here.
Standard atomic weights: CIAAW, the IUPAC commission; The atomic weights and their uncertainties, which is what an elemental analysis and a molar mass are built from. For a dozen elements the value is an interval rather than a number, because the isotopic composition of normal materials genuinely varies.
X-Ray Diffraction Procedures for Polycrystalline and Amorphous Materials: H. P. Klug and L. E. Alexander, Wiley, 2nd edition, 1974; The mass absorption coefficients behind the absorption calculator, for Z up to 83. It is also the standard account of powder diffraction as an experiment — specimen preparation, line broadening, quantitative analysis — which is the half this site does not compute.

Formats, dictionaries and structures

Where to look a definition up, and where to find a structure to put through the calculators here.

The CIF format: International Union of Crystallography; The specification and the data dictionaries for the file format the CIF parser reads.
Online Dictionary of Crystallography: International Union of Crystallography; Short, careful definitions, written by the people who set the terminology. Useful whenever a word on this site is doing more work than it looks like it is.
Crystallography Open Database: COD; Open-access crystal structures, as CIFs. A good source of real files to drop into the parser or the geometry page.

Why the sources are listed

A number is only as good as where it came from. Everything this site computes rests on the published work above, and the shipped datasets are generated from it by script — so a value here can be traced to a source, and a correction upstream reaches this site by rerunning a generator rather than by somebody retyping a table.

If a number on this site disagrees with one of these sources, the source is right and this site has a bug — please say so.