19
a
  \* o  o, /,.#
o o *\ o d/cP^/o
 T\ ? *
 ? \* r / o/ \ o
o/*yp/# o \*
\ o d'ji\d/o
-\*/ ei ,'jdj^r'm o 
V O  o
o
o Ni
Open circles: atoms in first and
third layers
Closed circles: atoms in second
layer
Figure 2.7 Two dimensional representation of Dla
stacking showing 1.) FCC unit cell ( ),
2.) Dla unit cell ( ), and 3.) 420 FCC
stacking sequence (  ).