The Crystal Structure of BaZn2Se2(OH)2 Featuring Brownmillerite‐Type Layers

Abstract

AbstractA bimetallic hydroxychalcogenide, BaZn2Se2(OH)2, was synthesized through hydrothermal pouch methods. The single crystal X‐ray diffraction and electron diffraction indicates that the phase crystallizes in the orthorhombic space group Pnma and is composed of anionic layers [ZnSe3/3(OH)1/1]− that are separated and charged balanced by Ba2+ cations. The [ZnSe3/3(OH)1/1]– layer comprises two unique Zn sites, which form interpenetrating zigzag chains with an in‐plane dipole moment and adopts a brownmillerite‐type structural motif. The adjacent layers contain tetrahedrally coordinated Zn chains of opposite handedness related by an inversion center, which cancel the microscopic dipoles to minimize the macroscopic electric polarization. The adoption of a brownmillerite structural motif in BaZn2Se2(OH)2 can be rationalized by the distinct charge difference between Se2− and OH− anions, which creates a sufficient dipole moment in the ZnSe3(OH) tetrahedra to allow the occurrence of twisted chains. FTIR spectroscopy confirms the existence of OH− anions and DFT calculations indicate that BaZn2Se2(OH)2 is a semiconductor with a direct band gap. This work expands the chemistry of the brownmillerite family from traditional homoanionic oxides to multianion hydroxychalcogenides, offering a new opportunity to explore tunable structural complexity for better design of functional materials.