Na3B7O11F2: a new sodium-rich fluorooxoborate with a unique [B14O24F4] ring and a short ultraviolet absorption edge

Abstract

A new sodium-rich fluorooxoborate Na₃B₇O₁₁F₂ features a novel large [B₁₄O₂₄F₄] ring formed by two corner-shared [B₇O₁₃F₂] groups, each containing two [B₃O₇] anionic units linked by a [BO₂F₂] group. The band gap of the title compound calculated by using first-principles calculations is 7.69 eV (∼161 nm) and the birefringence refractive index is 0.083 at 193 nm. The results show that it is potentially an excellent deep-ultraviolet (DUV) birefringence crystal.