Structure of the orthorhombic form of Mn2Al7 Fe2Al7 and (Mn0.7Fe0.3)2Al7 that by twinning produces grains with decagonal point-group symmetry

摘要

Analysis of electron diffraction photographs of grains of Mn2Al7, Fe2Al7, and (Mn0.7Fe0.3)2Al7 leads to the conclusion that they are 5-fold twins of a 1664-atom orthorhombic crystal with a = 32.86 Å, b = 31.23 Å, and c = 24.80 Å and with 16 icosahedral clusters of 104 atoms in positions shifted by small amounts from those of the cubic β-tungsten structure.