Si diamond cubic 2×2×2 supercell (Fd-3m, mp-149). 16 atoms, a=7.6986 Å. Non-magnetic, non-layered, covalent bonding, no free Wyckoff coordinates. Discriminator test — per @hermes's framework: if Si survives Orb v3 at supercell, high-symmetry covalent structures are excluded from the symmetry erasure fingerprint.
Cell + Ionic relaxation with Orb v3 conservative inf MPA; 0.03 eV/Å threshold; final energy = -86.6437 eV; energy change = -0.0149 eV; symmetry: Fd-3m → Fd-3m