Finding a Series of BaBOF₃ Fluorooxoborate Polymorphs with Tunable Symmetries: A Simple but Flexible Case

Abstract

Polymorphism is a subtle but important phenomenon in solid-state chemistry and material sciences. Generally, promoting the formation of a specific polymorph enables the modulation of symmetries and thus the optical properties, but the discovery of such polymorphs with tunable structures is extremely challenging. Herein, by focusing on the recently emerging fluorooxoborate system with a flexible skeleton, a series of new fluorooxoborate phases with the formula of BaBOF3 were obtained by a combined computational–experimental method. Among them, noncentrosymmetric α- and Cc-BaBOF3 phases show nonlinear optical effects and short deep-UV absorption edges, indicating that both compounds can be used as nonlinear optical materials. The small torsion and deformation in their anionic units, that is, [BO2F2] units, cause a huge difference in symmetry and thus in the nonlinear optical property. We demonstrated that the BaBOF3 polymorph with tunable structures and symmetries is a simple but perfect case to understand the influence of B–O/F interactions on creating new phases, which also enriches crystal chemistry of the species of fluorooxoborates. The first-principle calculations on the title compounds were performed to elucidate the structure–property relationship.

Na2BaB12O18F4: A Mixed Alkali/Alkaline-Earth Metal Fluorooxoborate with Two Unprecedented Interpenetrating Three-Dimensional B–O/F Anionic Networks and a Short Ultraviolet Cutoff Edge

“…The firstprinciples-assisted property computation on Na 2 BaB 12 O 18 F 4 was performed to explain the intrinsic mechanism between the microstructure and linear optical properties. Based on HSE06 method computation under the PWmat code, Na 2 BaB 12 O 18 F 4 exhibits a wide indirect electronic band gap, 7.30 eV (Figure 5a), which is close to the band gap of recently reported fluorooxoborates, such as α, β, γ-BaBOF 3 47 (E g = 7.01), Ba 2 B 7 O 12 F 30 (E g = 6.67 eV), and Na 2 B 6 O 9 F 2 33 (E g = 7.34 eV). The calculated band gap also corresponds well to the UV−vis− NIR diffuse reflectance data.…”

Na3YB8O15: a new rare-earth borate with an infinite one-dimensional [B8O15]∞chain and a short ultraviolet cutoff edge

“…The absorption bands appearing at around 685-512 cm −1 can be attributed to the bending vibrations of the BO 3 and BO 4 groups. [71][72][73][74] These characteristic peaks in the IR spectrum suggest the existence of both BO 3 and BO 4 groups in the structure of Na 3 YB 8 O 15 , which is consistent with the results of single crystal XRD.…”

γ-P4S3I2: a new metal-free infrared second-order nonlinear optical crystal designed by polymorphism strategy

“…20,21 Thus, many polymorphous borates and Pb-based compounds were reported, such as α-BaB 4 O 5 F 4 , α-BaBOF 3 , α-LiPbB 9 O 15 and β-PbGa 2 S 4 . [22][23][24][25] Moreover, using additives and adjusting temperatures were also helpful to obtain new polymorphs, for instance, β-Sc(IO 3 ) 3 26 can be obtained with Li 2 CO 3 as an additive. Besides, βand γ-BaGa 4 S 7 , β-BaGa 4 Se 7 and β-BaGa 2 Se 4 27,28 can be synthesized at differing appropriate temperatures.…”