Crystal structure of the monoclinic beta-Al11Cr2

The crystal structure of the monoclinic phase eta-Al11Cr2 of the space group C2/c, a approximate to 1.76 nm, b approximate to 3.05 nm, c approximate to 1.76 nm, beta approximate to 90 degrees [L.A. Bendersky, R.S. Roth, J.T. Ramon, D. Shechtman, Metall. Trans. A 22A (1991) 5] has been determined by single-crystal X-ray diffraction. The structure model, refined to a final R value of 0.0441, has the composition of Al83.8Cr16.2. a = 1.77348(10) nm, b = 3.04555(17) nm, c = 1.77344(10) nm, monoclinic angle beta = 91.0520(12)degrees. There are 80 (66Al + 14Cr) independent atomic positions in a unit cell, of which all Cr atom sites and 8 Al atom sites have icosahedral coordination. These icosahedra are interconnected forming icosahedral chains along [101], (101) icosahedral layer blocks as well as a three-dimensional icosahedral structure. (c) 2007 Elsevier B.V. All rights reserved.