Refinement of d-AlNiCo Quasicrystal Structures

摘要

The models of decagonal Al_(72)Ni_(20)Co_8 quasicrystal with the space group of P10_5/mmc were refined on the basis of single crystal x-ray diffraction data set using the 5D description. The results of a structure model derived from Al_(13)Fe_4-type approximant crystal and Burkov model are compared. The former gives w R=0.045 and R=0.063 for 449 reflections with 103 parameters and a reasonable chemical composition of Al_(71.2)TM_(28.8) (TM=transition metals). The projected structure is consistent with high resolution images of this material. On the other hand, the latter gives wR=0.161 and R=0.193 for 55 parameters and a composition of Al_(64.6)TM_(35.1).