BaB4O5F4 with reversible phase transition featuring unprecedented fundamental building blocks of [B16O21F16] in the α-phase and [B4O6F4] in the β-phase

Abstract

The first fluorooxoborate with reversible phase transition, BaB₄O₅F₄, has been obtained. Interestingly, the two polymorphs, α- and β-BaB₄O₅F₄ with rare [BOF₃], feature various one-dimensional chains composed of the unprecedented fundamental building blocks of [B₁₆O₂₁F₁₆] and [B₄O₆F₄], respectively. First-principles calculations were performed to elucidate the structure–property relationships.