XCrySDen can display properties such as charge densities, molecular orbitals, or any other 2D or 3D scalar field as isosurface or contours. This means, that a uniform 2D or 3D grid of points (containing the field values)---the grid does not need to be orthogonal---should be provided. Such grids are called Data Grids by XCrySDen. In order to display the isosurfaces/contours, the scalar field data should be written in XSF format. Here you can find the corresponding XSF description. The users of CRYSTAL and WIEN programs can achieve such plots also using the XCrySDen's interface for CRYSTAL and WIEN.

Once the XSF file is constructed, one should load it either as xcrysden --xsf my_file.xsf or via the File-->Open Structure ...-->Open XSF(Xcrysden Structure File) menu. Then proceed via the Tools-->Data Grid menu. The following window will appear:

This window plots schematically the structure of the scalar fields inputs. Namely, XSF file can contain several scalar fields. In the above example (i.e. figure of the window) the file contains only one scalar field. here is an example of window that corresponds to the file that contains several scalar fields:

In this example, three scalar fields are specified (see the three yellow-green rectangles, designated as sub-blocks). The first two are two-dimensional, and are mutual compatible, therefore they are specified within one block (i.e. block #0 on the figure). The third scalar field is three-dimensional. Here the user should specify which scalar field would like to plot. This is achieved by selecting (i.e. mouse-clicking) one radiobutton on orange block-rectangles. Then within a block one can select several scalar fields by mouse-clicking the corresponding checkbuttons on yellow-green subblock-rectangles. In above example two scalar fields are selected (see red checkbuttons on yellow-green subblock rectangles). A weight (i.e. multiply factor) for each selected scalar fields should be selected. Then the resulting scalar fields is calculated as:

F_res(r) = w(1)*F₁(r) + w(2)*F₂(r) + ...,

where w(i) is the weight (i.e. multiply factor) for i-th selected scalar field.

Once the scalar fields are selected and the weights are set, press the [OK] button. Then next window will appear, where various isosurface or contours parameters can be controlled. Here you can read how to control the display of the isosurfaces, and here you can get the description of how to control the display of contours.