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DOE OSTI2020

Materials Data on Eu3As4 by Materials Project

Eu3As4 crystallizes in the triclinic P1 space group. The structure is three-dimensional. there are six inequivalent Eu2+ sites. In the first Eu2+ site, Eu2+ is bonded to eight As+1.50- atoms to form corner-sharing EuAs8 hexagonal bipyramids. There are a spread of Eu–As bond distances ranging from 3.09–3.22 Å. In the second Eu2+ site, Eu2+ is bonded in a 8-coordinate geometry to eight As+1.50- atoms. There are a spread of Eu–As bond distances ranging from 3.07–3.18 Å. In the third Eu2+ site, Eu2+ is bonded in a 8-coordinate geometry to eight As+1.50- atoms. There are a spread of Eu–As bond distances ranging from 3.06–3.20 Å. In the fourth Eu2+ site, Eu2+ is bonded in a 8-coordinate geometry to eight As+1.50- atoms. There are a spread of Eu–As bond distances ranging from 3.08–3.23 Å. In the fifth Eu2+ site, Eu2+ is bonded in a 8-coordinate geometry to eight As+1.50- atoms. There are a spread of Eu–As bond distances ranging from 3.06–3.19 Å. In the sixth Eu2+ site, Eu2+ is bonded in a 8-coordinate geometry to eight As+1.50- atoms. There are a spread of Eu–As bond distances ranging from 3.07–3.20 Å. There are eight inequivalent As+1.50- sites. In the first As+1.50- site, As+1.50- is bonded in a 8-coordinate geometry to six Eu2+ and two As+1.50- atoms. There are one shorter (2.47 Å) and one longer (2.61 Å) As–As bond lengths. In the second As+1.50- site, As+1.50- is bonded in a 7-coordinate geometry to six Eu2+ and one As+1.50- atom. The As–As bond length is 2.54 Å. In the third As+1.50- site, As+1.50- is bonded in a 8-coordinate geometry to six Eu2+ and two As+1.50- atoms. There are one shorter (2.45 Å) and one longer (2.59 Å) As–As bond lengths. In the fourth As+1.50- site, As+1.50- is bonded in a 7-coordinate geometry to six Eu2+ and one As+1.50- atom. In the fifth As+1.50- site, As+1.50- is bonded in a 7-coordinate geometry to six Eu2+ and one As+1.50- atom. The As–As bond length is 2.54 Å. In the sixth As+1.50- site, As+1.50- is bonded in a 8-coordinate geometry to six Eu2+ and two As+1.50- atoms. In the seventh As+1.50- site, As+1.50- is bonded in a 8-coordinate geometry to six Eu2+ and two As+1.50- atoms. In the eighth As+1.50- site, As+1.50- is bonded in a 7-coordinate geometry to six Eu2+ and one As+1.50- atom.

36 MATERIALS SCIENCE↗

DOE OSTI2020

Materials Data on Eu3As4 by Materials Project

Eu3As4 crystallizes in the orthorhombic Fdd2 space group. The structure is three-dimensional. there are two inequivalent Eu2+ sites. In the first Eu2+ site, Eu2+ is bonded in a 8-coordinate geometry to eight As+1.50- atoms. There are a spread of Eu–As bond distances ranging from 3.12–3.23 Å. In the second Eu2+ site, Eu2+ is bonded in a 8-coordinate geometry to eight As+1.50- atoms. There are a spread of Eu–As bond distances ranging from 3.12–3.26 Å. There are two inequivalent As+1.50- sites. In the first As+1.50- site, As+1.50- is bonded in a 7-coordinate geometry to six Eu2+ and one As+1.50- atom. The As–As bond length is 2.53 Å. In the second As+1.50- site, As+1.50- is bonded in a 8-coordinate geometry to six Eu2+ and two As+1.50- atoms. The As–As bond length is 2.63 Å.

36 MATERIALS SCIENCE↗

DOE OSTI2024

Completing the Ba–As Compositional Space: Synthesis and Characterization of Three New Binary Zintl Arsenides, Ba3As4, Ba5As4, and Ba16As11

Three novel binary barium arsenides, Ba3As4, Ba5As4, and Ba16As11, were synthesized and their crystal and electronic structures were investigated. Structural data collected via the single-crystal X-ray diffraction method indicate that the anionic substructures of all three novel compounds are composed of structural motifs based on the homoatomic As–As contacts, with [As2]4− dimers found in Ba5As4 and Ba16As11, and an [As4]6− tetramer found in Ba3As4. Ba3As4 and Ba5As4 crystallize in the orthorhombic crystal system—with the non-centrosymmetric space group Fdd2 (a = 15.3680(20) Å, b = 18.7550(30) Å, c = 6.2816(10) Å) for the former, and the centrosymmetric space group Cmce (a = 16.8820(30) Å, b = 8.5391(16) Å, and c = 8.6127(16) Å) for the latter—adopting Eu3As4 and Eu5As4 structure types, respectively. The heavily disordered Ba16As11 structure was solved in the tetragonal crystal system with the space group P4¯21m (a = 12.8944(12) Å and c = 11.8141(17) Å). The Zintl concept can be applied to each of these materials as follows: Ba3As4 = (Ba2+)3[As4]6−, Ba5As4 = (Ba2+)5(As3−)2[As2]4−, and 2 × Ba16As11 = (Ba2+)32(As3−) ≈ 20[As2]4− ≈ 1, pointing to the charge-balanced nature of these compounds. Electronic structure calculations indicate narrow bandgap semiconducting behavior, with calculated bandgaps of 0.47 eV for Ba3As4, 0.34 eV for Ba5As4, and 0.33 eV for Ba16As11.

Crystallography↗