GATE 2020 MT – Question 13
A slip system consists of a slip plane and slip direction. Which is NOT valid in FCC copper?
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Correct answer: (B) $(\bar111)[011]$
Explanation
FCC slip uses {111} planes and ⟨110⟩ directions lying in those planes. Test the dot product of the plane normal (h,k,l) with the direction [u,v,w]; it must vanish. A, C and D give zero. For B, $(-1)(0)+(1)(1)+(1)(1)=2$, so its direction is not in the stated plane. Thus B is invalid.