Structure refinement of the icosahedral AIPdMn quasicrystal using quantitative CBED

Abstract

The atomic structure of the perfect AIPdMn icosahedral phase has been studied on a single crystal specimen by quantitative convergent beam electron diffraction (QCBED) technique in combination with describing the shape of atonic surface by symme try-adapted series of surface harmonics. The spherical model was used as the starting model for the refinement. By fitting the calculated electron diffraction intensities to the experimental line scan profile, the coefficients in the surface harmonics expansion of the boundaries of atomic surface are refined. The refined parameters show that the fluctuations of the external boundary of atomic surface for Pd atn0 can be as large as 0.2 nm. The boundaries of atomic surfaces for Mn show little fluctuation. In the present model. the number of unphysically short interatonic distances is significantly reduced in comparison with the spherical model.