XCrySDen is a crystalline- and molecular-structure visualisation program. The name of the program stands for Crystalline Structures and Densities and X because it runs under the X-Window environment. It facilitates a display of isosurfaces and contours, which can be superimposed on crystalline structures and interactively rotated and manipulated. It also possesses some tools for analysis of properties in reciprocal space such as interactive selection of k-paths in the Brillouin zone for the band-structure plots, and visualisation of Fermi surfaces.

The graphical user interface of XCrySDen was developed to provide an easy to use and learn interface. Casual users should be able to exploit more than just the basic functionality without devoting more than a few hours of effort to the task of learning the use of the program.

XCrySDen also provides a (partial) graphical user interface for CRYSTAL ab initio program, and a visualization system for Quantum ESPRESSO and WIEN2k programs.

Supported file formats

XCrySDen can read molecular (or crystal) structure from a few standard file formats such as XYZ, PDB, and its own internal XSF format.

In addition, it can visualise chemical structures for the following ab initio simulation software:

• Quantum ESPRESSO
• WIEN2k
• CRYSTAL
• GAUSSIAN
• Orca
• FHI98MD

External converting utilities

• Jens Kunstmann has written an XSF-converting tool xsfConvert. It can convert the data from the TB-LMTO-ASA and VASP programs to the XSF format.

• Andrei Postnikov has written Sies2xsf selection of routines for transforming SIESTA properties files into input files for the XCrySDen package. See README file and a PDF presentation.
  

• Michael Rutter has written c2x that reads and writes a selection of file formats which relate to DFT electronic structure codes. Formally, it was known as check2xsf, which converted the CASTEP binary .check file into the corresponding XSF file for plotting charge densities etc.

• XCrySDen can be also used for the visualization of data produced with the ABINIT program (e.g. Cut3D utility)

Molecular (and general) visualising features:

XCrySDen possesses more or less all the features that are expected from a modern molecular visualiser:

1. representation of molecular-models in several display modes (wireframe, sticks, ball-and-sticks, spacefill, ...)
2. display of forces acting on atoms
3. real time operations such as rotation, translation and zooming of displayed structure
4. animations
5. measurement of distances, angles, and dihedrals
6. contour-plane and isosurface representation of scalar fields
7. "arrows" representation of the vector field
8. setting various attributes, such as colours of atoms and bonds, radii of atoms, thicknesses of bonds and lines, sizes of points, balls and spacefills, just to name a few
9. and more ...

Crystalline visualising features:

In addition to the above described ``standard'' molecular visualising features, XCrySDen comes with an additional set of features that are necessary for visualising crystalline structures. Therefore XCrySDen is able to:

1. switch between primitive and conventional cell settings
2. change the number of the displayed unit cells, that is, display smaller or larger portions of a crystal
3. display the crystal lattice
4. visualise the Wigner-Seitz cell and Brillouin-zone
5. k-path selection for band-structure calculations
6. visualization of Fermi surfaces
7. and more ...

XCrySDen natively runs on GNU/Linux without any hardware requirements. It has been also ported to Mac OS (thanks to Mike Ford, David Strubbe, Hanspeter Niederstrasser, Marino Vetuschi Zuccolini, Tomohiko Tasaka, David Wood, and others), but requires X11. It can also run under Windows, but requires either the CYGWIN or WSL).

The compilation of the source package requires C and Fortran compilers as well as Tcl/Tk, Mesa (OpenGL), Togl, and FFTW3 libraries (development versions). These libraries are also needed to run dynamically compiled (shared) binary packages.