The reciprocal lattice unit cell of the monoclinic crystal is drawn in Fig. 6.6 in an
orientation where the a∗, b∗ and c∗ unit cell vectors and the reciprocal lattice points
at the corners can be seen clearly. Notice that the idea of ‘layers’ of reciprocal lattice
points applies (of course) to all orientations, for example the ‘bottom face’ of the cell
contains the hk0 reciprocal lattice points, the ‘top face’, one step along c∗ contains the
hk1 reciprocal lattice points—and so on.