The zone axis (ZA) is the direction lying in all the planes shown in
the slice of reciprocal space represented in the diffraction pattern, i.e. the vector
perpendicular to all the g vectors in
Take any two g vectors, g1 (h1k1l1)
and g2 (h2k2l2)
from the diffraction pattern. The zone axis is given by the vector product::
The zone axis is parallel (or nearly parallel) to the electron beam direction.