Step 1: Define the First Brillouin Zone.
The First Brillouin Zone is a core concept in solid-state physics, characterizing electron wave propagation within a crystal lattice.
Step 2: Evaluate each statement.
- A. Wigner-Seitz cell of reciprocal lattice: This is the standard definition of the First Brillouin Zone. The Wigner-Seitz cell is the space closest to one lattice point compared to any other. Applied to the reciprocal lattice, this defines the Brillouin zone. This statement is correct.
- B. Primitive unit cell: Due to its construction as a Wigner-Seitz cell, the First Brillouin Zone is a primitive unit cell of the reciprocal lattice, possessing the volume of one primitive cell. This statement is correct.
- C. The locus of all k-values...which are Bragg reflected: The boundaries of the Brillouin Zone are defined by planes that perpendicularly bisect vectors from the reciprocal lattice origin to nearest lattice points. These planes correspond to wave vectors (\(k\)-values) satisfying the Bragg diffraction condition, \(2\mathbf{k} \cdot \mathbf{G} = |\mathbf{G}|^2\). Consequently, the zone encompasses k-vectors not Bragg reflected, with its boundaries marking the onset of Bragg reflection. The statement accurately connects the zone to Bragg reflection.
- D. Wigner-Seitz cell of direct lattice: This is incorrect. The Wigner-Seitz cell of the *direct* lattice is a primitive cell in real space, not reciprocal space. The Brillouin zone is exclusively a concept pertaining to the reciprocal lattice.
Step 3: Conclude the correct statements.
Statements A, B, and C accurately describe the Brillouin zone. Statement D is incorrect. Therefore, the correct option comprises only A, B, and C.