Campus Units

Chemistry, Ames Laboratory

Document Type

Article

Publication Version

Published Version

Publication Date

2012

Journal or Book Title

Inorganic Chemistry

Volume

51

First Page

9395

Last Page

9402

DOI

10.1021/ic301196z

Abstract

The Na–Au–Zn system contains the two intermetallic phases Na0.97(4)Au2Zn4 (I) and Na0.72(4)Au2Zn2 (II) that are commensurately and incommensurately modulated derivatives of K0.37Cd2, respectively. Compound I crystallizes in tetragonal space group P4/mbm (No. 127), a = 7.986(1) Å, c = 7.971(1) Å, Z = 4, as a 1 × 1 × 3 superstructure derivative of K0.37Cd2 (I4/mcm). Compound II is a weakly incommensurate derivative of K0.37Cd2 with a modulation vector q = 0.189(1) along c. Its structure was solved in superspace group P4/mbm(00g)00ss, a = 7.8799(6) Å, c = 2.7326(4) Å, Z = 2, as well as its average structure in P4/mbm with the same lattice parameters.. The Au–Zn networks in both consist of layers of gold or zinc squares that are condensed antiprismatically along c ([Au4/2Zn4Zn4Au4/2] for I and [Au4/2Zn4Au4/2] for II) to define fairly uniform tunnels. The long-range cation dispositions in the tunnels are all clearly and rationally defined by electron density (Fourier) mapping. These show only close, somewhat diffuse, pairs of opposed, ≤50% occupied Na sites that are centered on (I) (shown) or between (II) the gold squares. Tight-binding electronic structure calculations via linear muffin-tin-orbital (LMTO) methods, assuming random occupancy of ≤ ∼100% of nonpaired Na sites, again show that the major Hamilton bonding populations in both compounds arise from the polar heteroatomic Au–Zn interactions. Clear Na–Au (and lesser Na–Zn) bonding is also evident in the COHP functions. These two compounds are the only stable ternary phases in the (Cs,Rb,K,Na)–Au–Zn systems, emphasizing the special bonding and packing requirements in these sodium structures.

Comments

This is an article from Inorganic Chemistry 51 (2012): 9395, doi: 10.1021/ic301196z. Posted with permission.

Copyright Owner

American Chemical Society

Language

en

File Format

application/pdf

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