Continuity chords of bands in solids: The diamond structure

The concept of a continuity chord is defined for denoting all those Bloch states at different symmetry points in the Brillouin zone that by symmetry and continuity can, in principle, belong to one band of a solid. The continuity chords for different bands are derived on the basis of band representations of space groups. A specific example of the diamond group ${O_h}^7$ is considered in detail and the continuity chords are calculated for all the possible symmetry types of bands for this group.