  We study four double-gyroid (DG) grain boundaries (GBs) with different
orientations numerically using the Landau--Brazovskii free energy, including
the (422) twin boundary studied recently, a network switching GB, and two tilt
GBs. Topological variations and geometric deformations are investigated. It is
found that deviations in strut lengths and dihedral angles from the bulk DG
substantially exceed changes in strut angles and nodal coplanarity. We also
examine the spectra along the contact plane of two grains and utilize them to
evaluate the GB widths. Of the four GBs we study, the network switching GB
changes to the least extent topologically and geometrically, meanwhile has the
lowest energy and the smallest GB width.
