Structure refinement of the icosahedral AlPdMn quasicrystal using quantitative convergent beam electron diffraction and symmetry-adapted parameters

• Published in: Journal of physics. Condensed matter 2003-07, Vol.15 (29), p.4947-4960
• Main Authors: Fang, Aihua, Zou, Huamin, Yu, Fengmei, Wang, Renhui, Duan, Xiaofeng
• Format: Article
• Language: English
• Subjects: Condensed matter: structure, mechanical and thermal properties; Exact sciences and technology; Physics; Quasicrystals; Semi-periodic solids; Structure of solids and liquids; crystallography
• ISSN: 0953-8984; 1361-648X
• DOI: 10.1088/0953-8984/15/29/306

The atomic structure of the perfect AlPdMn icosahedral phase has been studied on a single-crystal specimen using the quantitative convergent beam electron diffraction (QCBED) technique combined with a description of the shapes of atomic surfaces using a symmetry-adapted series of surface harmonics. The spherical model (Boudard et al 1992 J. Phys.: Condens. Matter 4 10149) was used as a starting point for the refinement. By fitting the calculated electron diffraction intensities in the CBED line profile to the experimental electron diffraction intensities, the coefficients in the surface harmonic expansion of the atomic surfaces' boundaries are refined. The refined parameters show that the fluctuations of the external boundary of atomic surface for Pd at no can be as large as 0.2 urn. The boundaries of the atomic surfaces for Mn show little fluctuation. Compared to the spherical model, in the present model the number of unphysically short interatomic distances is reduced significantly. The three-dimensional atomic clusters with centres located successively at the six-dimensional lattice nodes no, n1 and bc1, are generated by means of the cut method.