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Article
Experimental and Theoretical Studies of Elemental Site Preferences in Quasicrystalline Approximants (R-Phases) within the Li−Mg−Zn−Al System
Inorganic Chemistry
  • Chi-Shen Lee, Iowa State University
  • Gordon J. Miller, Iowa State University
Document Type
Article
Publication Version
Published Version
Publication Date
1-1-2001
DOI
10.1021/ic0008363
Abstract

A series of ternary and quaternary R-phase compounds in the Li−Mg−Zn−Al system are synthesized from pure elements in sealed Ta tubes with starting compositions based on the suggestions from electronic structure calculations using relative Mulliken populations to quantify the site preferences for the various elements. Single-crystal structural analyses reveal new R-phase compounds with various Li/Mg and Zn/Al ratios. The space group of all compounds is Im3̄ (No. 204). Five quaternary phases [Li1.00(1)Mg0.63(2)Zn1.23(1)Al2.14(1) (1), a = 14.073(3) Å; Li1.00(1)Mg0.63(1)Zn1.42(1)Al1.96(1) (2), a = 14.088(3) Å; Li1.01(1)Mg0.62(1)Zn1.31(1)Al2.06(1) (3), a = 14.096(5) Å; Li1.03(1)Mg0.60(1)Zn1.78(3)Al1.59(3) (4), a = 13.993(5) Å; Li0.78(2)Mg0.85(2)Zn2.47(1)Al0.94(1) (5), a = 13.933(2) Å] and four ternary compounds [Li1.63Zn0.81(1)Al2.56(1) (6), a = 14.135(3) Å; Li1.63Zn1.42(1)Al1.95(1) (7), a = 13.966(5) Å; Li1.63Zn1.59(1)Al1.78(1) (8), a = 13.947(2) Å; and Li1.63Zn1.77(1)Al1.60(1) (9), a = 13.933(4) Å] are identified. The crystal structure exhibits an Al/Zn (M sites) network constructed from M12 icosahedra and M60 buckyball-type clusters. Li/Mg atoms (A sites) fill cavities within the Al/Zn network to give pentagonal dodecahedra (A20). The site-potential studies (relative Mulliken populations) indicate two groups of atomic sites (positively and negatively polarized), which are consistent with the single-crystal studies. Further differentiation of site potentials among the various electropositive sites leads to segregation of Li and Mg, which is also verified experimentally. The analysis of relative Mulliken populations in an intermetallic framework provides a useful method for elucidating elemental site preferences when diffraction techniques cannot unequivocally solve the site preference problem.

Comments

Reprinted (adapted) with permission from Inorg. Chem., 2001, 40 (2), pp 338–345. Copyright 2001 American Chemical Society.

Copyright Owner
American Chemical Society
Language
en
File Format
application/pdf
Citation Information
Chi-Shen Lee and Gordon J. Miller. "Experimental and Theoretical Studies of Elemental Site Preferences in Quasicrystalline Approximants (R-Phases) within the Li−Mg−Zn−Al System" Inorganic Chemistry Vol. 40 Iss. 2 (2001) p. 338 - 345
Available at: http://works.bepress.com/gordon-miller/41/