Enantiomorph identification of transition-metal disilicides with the C40 structure (the space group of P6222 and P6422) by new convergent-beam electron diffraction method

The new CBED method we proposed recently for enantiomorph identification has been applied to transition-metal disilicides with the C40 structure (the space groups of P6222 and P6422). The enantiomorph can be easily identified by simply inspecting the intensity asymmetry of Bijvoet pairs of ZOLZ and/or FOLZ reflections in a CBED pattern taken along an appropriate zone-axis orientation. The way for enantiomorph identification with the present method is altered neither with the changes in the lattice parameters and averaged atomic scattering factors in the range expected for real C40 disilicide crystals of multi-component nor with the atom position parameter for Si atoms in 6j sites. The method is successfully applied to real C40 disilicides, and our single crystals of VSi2, CrSi2, TaSi2 and Mo(Si0.85Al0.15)2 are determined to belong to P6422 whereas that of NbSi2 is determined to belong to P6222. These results are all consistent with those of our previous X-ray diffraction study.