The γ-brass structure and the Boerdijk–Coxeter helix

Lord, EA and Ranganathan, S (2004) The γ-brass structure and the Boerdijk–Coxeter helix. In: 8th International Conference on Quasicrystals, SEP 08-13, 2002, Bangalore, INDIA.

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Abstract

The γ-brass structure was for a long time regarded as a modified bcc structure. It is more accurately described in terms of a 26-atom cluster consisting of four interpenetrating icosahedral clusters. An alternative description in terms of a 38-atom cluster is also illuminating. We discuss the γ-brass structure in terms of the packing of spheres and the packing of ‘almost regular’ tetrahedra and demonstrate a close relationship to the helical sphere packings investigated by Boerdijk, who considered the configuration of touching spheres centred at the vertices of a Coxeter helix, and extended it by adding an extra layer of spheres. Adding a further layer of spheres gives a rod-like structure in which every sphere of the original helix is surrounded by twelve others, configured as a somewhat distorted icosahedron. Thus each tetrahedron of the initial structure is then shared by four icosahedra. This 26-sphere cluster is a slightly distorted form of the 26-atom γ-brass cluster.

Item Type:	Conference Paper
Publisher:	Elsevier Science
Additional Information:	Copyright of this article belongs to Elsevier Science.
Keywords:	C200;M280;S440
Department/Centre:	Division of Mechanical Sciences > Materials Engineering (formerly Metallurgy)
Date Deposited:	08 Mar 2012 09:25
Last Modified:	08 Mar 2012 09:25
URI:	http://eprints.iisc.ac.in/id/eprint/43810

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