47
of the aforementioned antiphase boundaries are
indistinguishable.
2.3.4.1. P022: N3M0
There are three easily differentiated variants in the
DO22 structure, each corresponding to the c axis of the
DO22 being parallel to one of the cube axes of the parent
FCC lattice. This is shown in Figure 2.17a. All three
variants may be visible simultaneously. Indexed [001] and
[112] diffraction patterns are shown in Figure 2.19b.
2.3.4.2 Da: N4M0
Six distinguishable variants of Ni4Mo are possible.
These correspond to the tetrad axis of the Dla being
parallel to the parent FCC cube axes (three variants) and
further, the a axis of the N4M0 rotated cw or ccw about
the c axis relative to each FCC cube axis. Only two of
the six distinguishable variants will be visible along any
B = 100 imaging condition. These two are the single
axis clockwise and counterclockwise rotated variants shown
in Figure 2.18a. The B=[100] indexed diffraction pattern
corresponding to these two real space variants is shown in
Figure 2.18b. Indexed B = [001] and B = [112] N4M0
diffraction patterns are shown in Figure 2.19c.