Sb 5 O 7 I: Exploration of Ternary Antimony-Based Oxyhalide as a Nonlinear-Optical Material.

Metal oxyhalides are attracting extensive interest for their enchanting structures and diverse properties. Herein, a ternary antimony oxyiodide, Sb 5 O 7 I with the new hexagonal noncentrosymmetric P 6 3 structure is systematically surveyed by focusing on its nonlinear-optical (NLO) behavior. Its two-dimensional structure is constructed by {Sb 2 [Sb 3 O 7 ]} ∞ + layers separated by charge-balanced I - anions. The second-harmonic-generation measurement result suggests that Sb 5 O 7 I is NLO-active, and the effect is assigned to the [SbO 3 ] 3- triangular pyramids' contribution. Sb 5 O 7 I shows a direct optical energy gap of 3.22 eV, which is the largest among all reported ternary oxyiodides. This work is the first investigation of ternary NLO Sb-based oxyhalides and enriches the study of metal oxyhalides as promising NLO materials.