Ba 2 B 5 O 8 (OH) 2 (NO 3 )·3H 2 O: the design of an alkaline earth metal borate-nitrate optimized from a hydroxylic borate.

The first alkaline earth metal borate-nitrate, namely Ba 2 B 5 O 8 (OH) 2 (NO 3 )·3H 2 O (BBNOH), has been synthesized by the hydrothermal method. BBNOH crystallizes in the space group of P 2 1 / c and shows two-dimensional (2D) 2 ∞ [B 5 O 8 (OH) 2 ] 3- borate anion layers, and the hydrated barium cations and the [NO 3 ] - anions are located between the layers. The process of optimizing the structure of Ba 2 B 5 O 8 (OH) 2 OH to BBNOH has been discussed. The first principles calculation has been used to calculate the birefringence of Ba 2 B 5 O 8 (OH) 2 (NO 3 )·3H 2 O, and the value is 0.033@1064 nm, which is mainly originated from the borate anions and the π conjugated [NO 3 ] - anions.