M3B6O10NO3 (M = K, Rb): Two New Alkali Metal Borate‐Nitrates with Noncentrosymmetric Structures

Abstract Two new alkali metal borate‐nitrates, M 3 B 6 O 10 NO 3 (M = K, Rb), with noncentrosymmetric space groups P 3 1 21 and P 3 2 21, respectively, have been synthesized successfully through the high‐temperature solution method in sealed quartz tubes. Both crystals feature the frameworks with large channels along the c ‐axis, in which the chains locate. K 3 B 6 O 10 NO 3 presents a moderate phase‐matching powder second harmonic generation (SHG) response with a UV cut off edge of about 216 nm. The first principles calculations for both compounds have been executed to estimate the optical properties and deeply analyze the relationship between their structures and properties.