C2x, or check2xsf as it was first known, was developed in the TCM Group in Cambridge. It reads and writes a selection of file formats which relate to DFT electronic structure codes. It is not simply a conversion utility, but it can also perform manipulations and some analysis. It can form supercells and find primitive cells. If linked with the excellent spglib symmetry finder, it provides access to functionality from that package. It can interpolate densities via a combination of trilinear and Fourier interpolation, integrate densities and calculate their dipole moments, and analyse bands for inversion symmetry.
Originally supporting just Castep, c2x now supports Abinit, Onetep, Quantum Espresso, Siesta and VASP as well. It 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.
One use of c2x is extracting volumetric data (charge density, colinear spin density, or charge density from a given band) for visualisation. It supports output formats compatible with XCrysDen, VESTA, VMD and Jmol amongst others, and can also produce 1D data in a format suitable for gnuplot. The ethene π bond above is from the 2016 version of XCrysDen.
Another use of c2x is to use one package's post-processing tools
with another's. It can, for instance, convert a
.check file into a
readable by VASP post-processors.
C2x can be downloaded from its downloads page, as source or MacOS or Linux binaries.
Version 2.32 released, 12th December 2019. Adds ability to create nanotubes and perform averaged radial plots on them. Improvements to Siesta support, a sign change in the reading of .cst_esp files, the addition of a CCP4 writer, arbitrary rescaling of grid data, and much else. See Change Log for fuller details. Also some webpages giving simple examples of creating isosurfaces with different software.
Version 2.30c released, 6th November 2019. Mostly minor bug fixes.
Version 2.30 released, 16th August 2019. Significantly more features: reads wavefunctions from Abinit, VASP and QE, and adds an option to add (or change) vacuum gaps in structures. See Change Log for further details.
Version 2.29 released, 5th July 2019. Mostly to fix a regression in 2.28 which caused some cell transformations to fail with an error. Also now retains considerably more when converting a Quantum Espresso .in file to a Quantum Espresso .in file.
Version 2.28 released, 10th June 2019. (Improves dipole corrections, fixes some cell transformation bugs which bite if tolerance (-e) is a large number.)
Version 2.26b released, 2nd April 2019. (Improves Quantum Espresso support, adds new snap to symmetry option.)
Version 2.25 released, 22nd February 2019. (Adds calculation of some post-hoc dipole energy corrections. Also other minor improvements.)
Version 2.20a released, 11th February 2019. (Some bug fixes and cosmetic tidying.)
Version 2.20 released, 17th August 2018. (Adds calculation of electrostatic potential, rescales .cst_esp files by default.)
Version 2.16 released, 19th June 2018. (Adds reporting of band inversion and parity and initial Quantum Espresso support. Improves fdf support.)
Version 2.14 released, 27th March 2018. (Initial support for Abinit, improvements to .cube and Crystal support.)
Version 2.11 released, 2nd February 2018. (Adds dipole calculation, supports arithmetic expressions in .cell files.)
Source code of 2.05b made public, 12th December 2017, thus keeping a promise that it would be released in 2017.
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, 225 174-179 (2018). Once such papers are noticed, they are added to this list.