Crystal structures — BCC description: “In a body-centred cubic (BCC) space lattice, atoms appear at all eight cube corners with an additional atom at the cube centre.” Is this descriptive statement acceptable in crystallography textbooks?

Introduction / Context:
Unit-cell descriptions use idealised atom positions to convey symmetry. For the BCC lattice, the standard verbal description mentions atoms at the eight corners and one at the body centre. Although the effective atom count per unit cell is two, the positional description with nine sites is widely taught.

Given Data / Assumptions:

• We are evaluating the correctness of the positional description for BCC.
• Corner atoms are shared among eight adjacent cubes.
• The body-centre atom belongs wholly to the unit cell.

Concept / Approach:
The BCC lattice points: eight corners + one body centre. Counting contributions: each corner contributes 1/8 to a cell → total corner contribution = 8 * (1/8) = 1 atom, plus the single body-centre atom = 1 atom → total effective = 2 atoms per unit cell. Therefore the positional statement is acceptable and standard, even though atom counting for density uses the effective count of two.

Step-by-Step Solution:
State positional description: 8 corners + 1 centre.Convert positions to effective count: 8*(1/8) + 1 = 2 atoms per cell.Conclude description is correct for BCC symmetry and teaching.Hence, answering “Yes” is appropriate.

Verification / Alternative check:
Textbooks on crystallography and materials science use exactly this wording for BCC (e.g., ferrite in steels at room temperature).

Why Other Options Are Wrong:
“No” or “faces only” misstates the BCC geometry; the faces-only description corresponds to FCC, not BCC.

Limiting to alpha-iron is unnecessary; BCC is a general lattice type.

While the note about “exactly two atoms per unit cell effectively” is true, it does not invalidate the positional description.

Common Pitfalls:
Confusing geometric positions with effective atom count; mixing up BCC and FCC arrangements.

Final Answer:
Yes