  We present a new complementary strategy to quasicrystalline structure
determination: The local atomic structure of simple icosahedral (si)
Ho11Mg15Zn74 [a(6D)=5.144(3)A] in a sphere of up to r=17A was refined using the
atomic pair distribution function (PDF) from in-house X-ray powder diffraction
data (MoKa1, Qmax=13.5A-1; R=20.4%). The basic building block is a 105-atom
Bergman-Cluster {Ho8Mg12Zn85}. Its center is occupied by a Zn atom - in
contrast to a void in face centred icosahedral (fci) Ho9Mg26Zn65. The center is
then surrounded by another 12 Zn atoms, forming an icosahedron (1st shell). The
2nd shell is made up of 8 Ho atoms arranged on the vertices of a cube which in
turn is completed to a pentagon dodecahedron by 12 Mg atoms, the dodecahedron
then being capped by 12 Zn atoms. The 3rd shell is a distorted soccer ball of
60 Zn atoms, reflecting the higher Zn content of the si phase compared to the
fci phase. In our model, 7% of all atoms are situated in between the clusters.
The model corresponds to a hypothetical 1/1-approximant of the icosahedral (i)
phase. The local coordinations of the single atoms are of a much distorted
Frank-Kasper type and call to mind those present in 0/1-Mg2Zn11.
