about the entire system L+C+R should be periodic

[fanjiaping]

      as we know,if in fcc [111]:
• [ABC]AB–...–BC[ABC] (no mirror, no stacking fault)
• [ABC]AB–...–BA[CBA] (mirror, bad stacking fault BAAB)
• [ABC]AB–...–BAC[BAC] (mirror, minor stacking fault ACAB)
but if in fcc[1 0 0]:
there is only ABABAB.no matter how we set the L+C+R,there must be a mirror in the system.In this case,how can we deal with?or we can use the [1 0 0]in face center cubic?
                                                                                    thank you!

[Anders Blom]

Sure, no problem. The mirror symmetry is not the issue, it's the stacking fault (= broken periodicity in the Z direction) which is problematic.