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Crystal structures and Miller indices

Which correctly pairs the close-packed planes and close-packed directions of an FCC metal?

  1. A{110} planes and <111> directions
  2. B{111} planes and <110> directions
  3. C{100} planes and <100> directions
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Answer: B. {111} planes and <110> directions

In FCC, the {111} planes are the most densely packed, and within them atoms touch along the face diagonals, the <110> directions. Slip in FCC metals occurs on {111}<110>; there are 4 kinds of {111} plane, each with 3 <110> directions, giving 12 slip systems. {110} planes and <111> directions are the densest plane and direction in BCC, a pairing that is easily confused with FCC. {100} planes and <100> directions are the densest plane and direction in SC and are not close-packed in FCC.

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More Crystal structures and Miller indices questions

  1. Which value is closest to the interplanar spacing of the (111) planes of aluminum (FCC, lattice parameter 0.405 nm)?
  2. Which statement about the ideal hexagonal close-packed (HCP) structure is correct?
  3. In a cubic crystal, which value is closest to the angle between the [100] and [111] directions?
  4. At 912 °C, pure iron transforms from BCC α-iron (lattice parameter 0.2904 nm) to FCC γ-iron (lattice parameter 0.3647 nm). Which correctly describes the change in volume per atom? Both lattice parameters are values at 912 °C.
  5. In a face-centered cubic (FCC) metal, how many atoms touch a given atom at the nearest-neighbor distance (the coordination number)?