Network Formation by Condensed Tetrahedral [Au3Al] Units in Na2Au3Al: Crystal and Electronic Structure, Spectroscopic Investigations, and Physical Properties of an Ordered Ternary Auride

Frank Stegemann; Christopher Benndorf; Yuemei Zhang; Manfred Bartsch; Helmut Zacharias; Boniface P T Fokwa; Hellmut Eckert; Oliver Janka

doi:10.1021/acs.inorgchem.6b02480

Network Formation by Condensed Tetrahedral [Au₃Al] Units in Na₂Au₃Al: Crystal and Electronic Structure, Spectroscopic Investigations, and Physical Properties of an Ordered Ternary Auride

Inorg Chem. 2017 Feb 20;56(4):1919-1931. doi: 10.1021/acs.inorgchem.6b02480. Epub 2017 Jan 31.

Authors

Frank Stegemann¹, Christopher Benndorf^{1

2}, Yuemei Zhang³, Manfred Bartsch⁴, Helmut Zacharias⁴, Boniface P T Fokwa³, Hellmut Eckert^{2

5}, Oliver Janka^{1

6}

Affiliations

¹ Institut für Anorganische und Analytische Chemie, Westfälische Wilhelms-Universität Münster , Corrensstrasse 28, D-48149 Münster, Germany.
² Institut für Physikalische Chemie, Westfälische Wilhelms-Universität Münster , Corrensstrasse 30, D-48149 Münster, Germany.
³ Department of Chemistry, University of California, Riverside , 501 Box Springs Rd, Riverside, California 92521, United States.
⁴ Physikalisches Institut, Westfälische Wilhelms-Universität Münster , Wilhelm-Klemm-Strasse 10, D-48149 Münster, Germany.
⁵ Instituto de Física de São Carlos, Universidade de São Paulo , São Carlos-SP 13566-590, Brazil.
⁶ Institut für Chemie, Carl von Ossietzky Universität Oldenburg , Carl-von-Ossietzky Strasse 9-11, D-26129 Oldenburg, Germany.

PMID: 28140577
DOI: 10.1021/acs.inorgchem.6b02480

Abstract

Na₂Au₃Al, the first experimentally prepared compound in the ternary Na-Au-Al system, crystallizes in the cubic crystal system with space group P4₁32 (a = 771.42(2) pm). It can be described as a P-centered ternary ordered variant of the F-centered Laves phase MgCu₂ and is isostructural to Mo₃Al₂C. A phase width was found for the series Na₂Au_4-xAl_x allowing a successive substitution of Au by Al. The primitive structure forms for x ≥ 0.5. Na₂Au₃Al is diamagnetic at room temperature but metallic in nature, as seen from susceptibility and electrical resistivity measurements. Band structure calculations and X-ray photoelectron spectroscopy confirm the metallic nature of the title compound as states are found at the Fermi level of the DOS, along with its "auride" character. ²³Na and ²⁷Al solid-state-NMR investigations show the existence of both a disordered (x = 0.5 and 0.75) and a fully ordered (x = 1.0) representative within this series. Both COHP and Bader charge analyses suggest the presence of strong Au-Al interactions forming an anionic [Au₃Al]^δ- network, with the Na cations occupying the cavities.