Crystal structure of KBe2BO3F2

Abstract

Abstract Potassium beryllium borate fluoride, KBe2 · BO3F2, is rhombohedral (hexagonal axes) R32 (No.155), a = b = 4.427(4) Å, c = 18.744(9) Å, V = 318.3(4) Å3, M = 153.93, D m = 2.40g · cm−3, D x = 2.41 g · cm−3 for Z = 3, F(000) = 222, μ = 11.84 cm−1, T = 296 K. The crystal structure has been determined by single crystal X-ray diffraction and final R value for 260 unique reflections with I > 3σ(I) is 3.1%. The results reveal a new type of complex polyanions. All B atoms are planar triangularly coordinated while all Be atoms are tetrahedrally coordinated. The feature of the borate framework is infinite sheets [Be2BO3F2] which may be described in terms of six-membered rings of [Be2BO6F2] having Be–O and B–O edges in common. The nonlinear optical(NLO) properties of this compound are also discussed here and the [BO3]3− anionic groups are principally responsible for the second harmonic generation (SHG) effect.