Question

The close packing sequence ABABAB in 3-D represents which of the following?

• A. Primitive Cubic Close packing
• B. Body-centered Cubic Close packing
• C. Face-centered Cubic Close packing
• D. Hexagonal Close Packing

Answer 1

Answer: (B), (D)

The correct options are
B

Body-centered Cubic Close packing

D

Hexagonal Close Packing

This is slightly tricky.

Do you remember what A and B represent?

They represent the 2-D close-packed layer with which we build our 3-D close-packed structures. Recall that these could either be square 2-D close-packed or hexagonal 2-D close-packed.

If we use the square 2-D close-packed layer and make ABAB type structure, we will end up with BCC.

This is option B.

If we use the hexagonal 2-D close packed layer and make ABAB type structure, we will end up with HCP.

This is option D.