Crystal structures – body-centred cubic (BCC) occupancy In a body-centred cubic crystal structure, the eight corners and the cube centre are occupied by identical atoms. Is this statement correct?

Introduction:
Crystallography describes how atoms are arranged in repeating unit cells. Recognizing simple structures such as simple cubic, body-centred cubic (BCC), and face-centred cubic (FCC) is fundamental for interpreting material properties like packing efficiency, slip systems, and mechanical behaviour.

Given Data / Assumptions:

• Ideal, perfect crystal without defects.
• Atoms identical at lattice points for an elemental BCC solid (e.g., α-iron at room temperature).
• Unit cell description according to conventional crystallography.

Concept / Approach:

In BCC, lattice points are at the eight cube corners and at the body centre. When atoms occupy these lattice points, the conventional picture is “corners plus centre” occupied by identical atoms for pure elements. Effective atom count per cell is 2 (8 corners × 1/8 + 1 centre × 1 = 2). This contrasts with FCC, which has atoms at corners and face centres (effective count 4).

Step-by-Step Solution:

Verification / Alternative check:

X-ray diffraction and crystallographic databases confirm BCC lattice for α-Fe, showing the body-centred atom.

Why Other Options Are Wrong:

“False” contradicts the BCC definition; the qualifier “only at 0 K” is unnecessary; centre is not empty in the occupied BCC lattice of pure metals.

Common Pitfalls:

Confusing BCC with simple cubic or FCC; miscounting atoms per unit cell.

Final Answer:

True