Face-Centered Cubic (FCC)
Features atoms at all 8 corners and at the center of each of the 6 faces. This is a close-packed structure, meaning it's very dense. Many common metals like Copper, Aluminum, Silver, and Gold have this structure.
The First Brillouin Zone
The shape you see is the Brillouin Zone, which is the fundamental 'unit cell' of reciprocal space. It's a map used by physicists to plot a material's electronic band structure and phonon dispersion. Its complex shape (like this truncated octahedron for FCC) is a direct consequence of the crystal's symmetry.
High-Symmetry Path
The labeled points (Γ, X, L, etc.) are special locations of high symmetry. The yellow line traces a standard path between them. Scientists calculate material properties along this path, as seen in the x-axis of the phonon plot.
