The crystal structure of a W-(AlCoNi) phase, which is closely related to Al-Co-Ni decagonal quasicrystals, has been studied by the single crystal X-ray diffraction. The W-(AlCoNi) phase was obtained from an Al72.5Co20Ni7.5 alloy sample annealed at 950 °C and its structure indicates the space group Cm (No. 8) with lattice parameters a=39.668(3) Å, b=8.158(1) Å, c=23.392(1) Å and β=90.05(1)°. A structural model with R(F) less than 0.087 for the observed 16 200 reflections can reproduce contrasts of atomic scale images obtained by high-angle annular detector dark-field scanning transmission electron microscopy together with high-resolution electron microscopy. The structure of the W-(AlCoNi) phase provides a fundamental atomic arrangement for the columnar atom cluster observed commonly in the Al-Co-Ni decagonal quasicrystals, and makes it possible to derive a structural model for the structures of the Al-Co-Ni decagonal quasicrystals.
- Crystalline approximant
- Single-crystal X-ray diffraction