Structure ofμ-MnAl4, a crystalline phase with composition close to that of quasicrystalline phases

The structure of $\mu$-Mn${\mathrm{Al}}_4$ has been determined by single-crystal x-ray diffraction. The space group is $\frac{{P6\mathrm{}}_3}{\mathrm{mmc}}$, $a=19.98\mathrm{}\left(1\right)\mathrm{}$, $c=24.673\mathrm{}\left(4\right)\mathrm{}$ ÅA, with 563 atoms per cell (average), and the formula is Mn${\mathrm{Al}}_{4.12}$. Parts of the structure resemble that of $\phi$-${\mathrm{Mn}}_3$ ${\mathrm{Al}}_{10}$. Neither complete Mackay icosahedra (MI), nor Bergman polyhedra are present, but different fragments of MI occur. Mn atoms have 0 to 2 Mn atoms in the first coordination shell and 4 to 12 Mn atoms in the second shell. The predominant coordinations are, for Mn, icosahedron; for Al, bicapped pentagonal prism, other CN(12) configurations, and CN(13).