Crystal Growth of K2HCO3F·H2O with a Very Short Cutoff Edge and Large Birefringence

Huge crystals of K 2 HCO 3 F·H 2 O promising for deep-ultraviolet birefringent materials have been grown via a facile aqua-solution method, and the related properties are reported for the first time. K 2 HCO 3 F·H 2 O revealing a parallel arrangement of [HCO 3 ·F·H 2 O] 2– chains along the c -axis exhibits a large experimental birefringence of 0.093 @589.6 nm. With the aid of the coexisting HCO 3 – and F – groups, the reported material exhibits a very short cutoff edge shorter than 195 nm. Theoretical calculations reveal that the observed large birefringence of the title compound originates from the synergistic effect of the aligned HCO 3 – and H 2 O groups.