Investigation of the surface terminations of icosahedral AlPdMn quasicrystal based on a modified non-spherical model

• Published in: Journal of physics. Condensed matter Vol. 16; no. 39; pp. 6821 - 6834
• Main Authors: Yu, Fengmei, Zou, Huamin, Wang, Jianbo, Wang, Renhui
• Format: Journal Article
• Language: English
• Published: Bristol IOP Publishing 06.10.2004; Institute of Physics
• Subjects: Condensed matter: structure, mechanical and thermal properties; Exact sciences and technology; Physics; Quasicrystals; Semi-periodic solids; Structure of solids and liquids; crystallography; Atomic position; Fibonacci sequences; Ternary alloys; Experimental study; Quasicrystals; Cluster model; Structural models; Icosahedral phase; Thin films; Surface termination; Aluminium alloys; Corrugated surface; Palladium alloys; Manganese alloys; Chemical composition
• ISSN: 0953-8984; 1361-648X
• DOI: 10.1088/0953-8984/16/39/015

The atomic positions are obtained from a modified non-spherical model of icosahedral AlPdMn quasicrystal (Fang et al 2003 J. Phys.: Condens. Matter 15 4947) by the cut method. The four-shell pseudo-Mackay clusters (PMCs) were searched for in a box of 400 A x 400 A x 400 A. The results show that the number of atoms in the fourth shell, an icosidodecahedron, of the pseudo-Mackay cluster can vary from 15 to 30 because of the cluster overlap, and about 99.96 percent of the total atoms are included in such incomplete pseudo-Mackay clusters. The characteristics of the atom distribution in the planes perpendicular to a fivefold axis indicate that the planes, which are 1.56 A apart from their neighbouring planes, are expected to be the terminal surfaces. If one such a plane and its closest neighbouring plane, between which the spacing is 0.48 A, are considered as a thin layer or a corrugated surface, these layers are also the layers with the maximum density. The pair of corrugated surfaces that are 1.56 A apart have almost identical chemical composition. These planes form terraces that follow the rule of the Fibonacci sequence with two step heights, 6.60 and 4.08 A. On the corrugated surfaces perpendicular to a fivefold axis the pentagonal holes arise from the interspaces of adjacent incomplete PMCs. For the atomic planes normal to a twofold axis, the planes with spacing of 1.48 A from their adjacent planes might be expected to be the terminal surfaces, which form terraces with step heights of 6.28 and 3.88 A following the rule of the Fibonacci sequence. For the atomic planes normal to a threefold axis, the planes with spacing of 0.86 A from their adjacent planes might be expected to be the terminal surfaces. No similar results were found for the atomic layers perpendicular to a pseudo-twofold axis.