ShelXleis a graphical user interface forSHELXL[Sheldrick, G. M. (2008).Acta Cryst.A64, 112–122], currently the most widely used program for small-molecule structure refinement. It combines an editor with syntax highlighting for theSHELXL-associated .ins (input) and .res (output) files with an interactive graphical display for visualization of a three-dimensional structure including the electron density (F_o) and difference density (F_o–F_c) maps. Special features ofShelXleinclude intuitive atom (re-)naming, a strongly coupled editor, structure visualization in various mono and stereo modes, and a novel way of displaying disorder extending over special positions.ShelXleis completely compatible with all features ofSHELXLand is written entirely in C++ using the Qt4 and FFTW libraries. It is available at no cost for Windows, Linux and Mac-OS X and as source code.

MoleCoolQtis a molecule viewer for charge-density research. Features include the visualization of local atomic coordinate systems in multipole refinements based on the Hansen and Coppens formalism as implemented, for example, in theXDsuite. Residual peaks and holes fromXDfftare translated so that they appear close to the nearest atom of the asymmetric unit. Critical points from a topological analysis of the charge density can also be visualized. As in the programMolIso, color-mapped isosurfaces can be generated with a simple interface. Apart from its visualization features the program interactively helps in assigning local atomic coordinate systems and local symmetry, which can be automatically detected and altered. Dummy atoms – as sometimes required for local atomic coordinate systems – are calculated on demand;XDsystem files are updated after changes. When using the invariom database, potential scattering factor assignment problems can be resolved by the use of an interactive dialog. The following file formats are supported:XD,MoPro,SHELX,GAUSSIAN(com, FChk, cube), CIF and PDB.MoleCoolQtis written in C++ using the Qt4 library, has a user-friendly graphical user interface, and is available for several flavors of Linux, Windows and MacOS.