UoC crest


ethene pi bond

C2x, or check2xsf as it was first known, was originally written to convert CASTEP's .check files into .xsf files viewable with XCrysDen. It thus provided a means of viewing isosurfaces from CASTEP without needing to purchase the commercial, Windows-only, Materials Studio front end.

Since then this utility has grown considerably in functionality. Version one grew to read .check, .castep_bin, .chdiff, .cell and .pdb files, and write .cell, .cml, .pdb, .xyz, Gnuplot and .cube files. It can form supercells, generate k-point meshes, find primitive cells, and generate k-points. It can extract band energies and k-point positions from .check files. It can perform both Fourier and trilinear interpolation to plot densities on given lines through cells. It has some degree of support for writing .fdf, SHELX97 and .cif files, and reading .res files.

Version two, renamed c2x to reflect the growing functionality beyond simply converting .check files to .xsf files, added support for VASP and Onetep, and also integrates with the excellent spglib symmetry finder, and provides access to functionality from that package. This represents a merging of check2xsf with cellsym.

It has also grown support for more electronic structure codes, and thus can be considered to be a little like OpenBabel, but with an emphasis on different codes, and support for volumetric data. List of supported formats.

This document was originally written around XCrysDen, but Jmol is now a good choice as well. XCrysDen has improved its image quality since many of these pages were written: the ethene π bond above is from a recent (2016) version of XCrysDen.

Getting c2x

Version 2 of c2x can be downloaded from this downloads page, as source or MacOS or Linux binaries.


Version 2.11 released, 2nd February 2018.

Source code of 2.05b made public, 12th December 2017, thus keeping a promise that it would be released in 2017.


Is entirely voluntary, for check2xsf is distributed under the GPL. However, if you wish to drop the author an email saying that you are using it, he can add you to an email list to which new versions and bug fixes are announced, and he will be able to justify spending more time on this software. You really have nothing to lose! mjr19

Citing c2x

If you find it useful in your published research, the traditional academic acknowledgement of a citation would be appreciated. C2x: a tool for visualisation and input preparation for Castep and other electronic structure codes, MJ Rutter, Computer Physics Communications, 225C 152-157 (2018).