CaRIne 4.0 includes new tools to create and visualize in an interactive way surfaces. A *surface* is defined from a unit cell, a (hkl) reference plane and some geometric properties. The graphic representation of a surface is not a surface in the mathematical meaning of the word, a third dimension is added to visualise a *box* and not a plane. Actually, a surface is built in a volume V (right-angled parallelepiped) for which the size is given in Angstroms. The length and the width of the volume V are taken in the (hkl) reference plane, and both thickness (upper and bottom) are taken respectively along the normal of the (hkl) reference plane and the inverted normal.

The (hkl) reference plane set automatically the orientation of the unit cell reference frame in the volume V, but it is always possible to rotate the unit cell along the normal of the (hkl) reference plane.

In order to set this last rotation possibility, a [uvw] direction (or one of the three lattice vectors) can be used. The angle between the reference axis of the surface and the projection of the [uvw] direction on the (hkl) reference plane must be given in degrees (°).

Finally, a surface can be calculated with a *cut defect*. A cut axis must be given, this cut axis can be every [uvw] direction taken in the (hkl) reference frame or not. During the building of the surface for which the cut defect is activated , the atoms and the lattice points are rotated around the cut axis, the angle of rotation must be given in degrees (°).

A surface is automatically updated, by a refresh event or a building event, if its associated unit cell (the one from which the surface is defined) is modified. In a project, several surfaces can be created from the same unit cell.