Crystal and Electronic Structure of Ba12Ga15As22

TL;DR

This paper reports the synthesis and structural analysis of a new Zintl phase, Ba12Ga15As22, revealing its unique crystal structure and semiconducting properties.

Contribution

The discovery of a new structure type for Ba12Ga15As22 and its electronic properties for potential thermoelectric applications.

Findings

Ba12Ga15As22 crystallizes in a monoclinic system with a previously unreported structure type.

The material exhibits a theoretical band gap of approximately 0.61 eV, indicating semiconducting behavior.

The structure contains [Ga2]4+ bonds and [GaAs4] tetrahedra chains, confirmed by X-ray and synchrotron diffraction.

Abstract

The novel ternary Zintl phase Ba12Ga15As22 was synthesized and structurally characterized. Structural data collected via single-crystal X-ray diffraction methods revealed the presence of homoatomic [Ga2]4+ bonds embedded within chains of edge- and corner-sharing [GaAs4] tetrahedra. Synchrotron powder diffraction data, processed via Rietveld refinement, further confirm the structural model. Ba12Ga15As22 crystallizes in the monoclinic crystal system with space group P21/c (a = 13.3334(10), b = 20.6392(16), c = 20.0336(15), β = 108.7168(14)) and adopts a previously unreported structure type. Ba12Ga15As22 is heavily disorder and its charge-balance can be described using the Zintl concept as follows: Ba12Ga15As22 = (Ba2+)12(Ga3+)12([Ga2]4+)1.5(As3–)22. Electronic structure calculations were performed to further investigate the bonding and electronic properties, motivated by expectation of semiconducting properties and suitability for thermoelectric applications.

Ba12Ga15As22 was found to exhibit a theoretical band gap of approximately 0.61 eV.