The GATE Grind

GATE 2024 MT – Question 30

Materials Science and Non-Metallic Materials · Crystal structures and bonding · 1 mark · Multiple select

Which (h k l) reflections are allowed in an X-ray diffraction pattern of a crystal with an FCC lattice?

  1. (0 0 1)
  2. (0 1 1)
  3. (1 1 1)
  4. (0 0 2)

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Correct answer: (C) (1 1 1); (D) (0 0 2)

Explanation

The FCC structure factor is nonzero only when h,k,l are all odd or all even, counting zero as even.

Thus (111) and (002) are allowed; (001) and (011) have mixed parity and are extinct.

Therefore **C,D**.