Structural Modulation of Nitrate Group with Cations to Affect SHG Responses in RE(OH)₂NO₃ (RE = La, Y, and Gd): New Polar Materials with Large NLO Effect after Adjusting pH Values of Reaction Systems

A series of rare-earth hydroxide nitrate crystals (La­(OH)₂NO₃, Y­(OH)₂NO₃, and Gd­(OH)₂NO₃) have been synthesized through adjusting pH values of reaction systems under the subcritical hydrothermal condition. All the titled compounds were isostructural with the noncentrosymmetric space group P2₁ (No. 4) with layer structure, containing [REO₉] (RE = La,Y, and Gd) polyhedra in each layer. The polyhedra were stacked on top of each other and further connected with zigzag strings of edge sharing to form infinite corrugated sheets that parallel to the a–c plane. The [NO₃] groups that presented two different orientation (A and B) project into the space between the layers. In this study, the angle θ between two different orientation [NO₃] groups was defined. With the decrease of ionic radii from La³⁺, Gd³⁺ to Y³⁺, the θ was increased, which led to different second harmonic generation (SHG) effects on lanthanide hydroxide nitrates. The powder SHG measurements revealed that La­(OH)₂NO₃, Gd­(OH)₂NO₃, and Y­(OH)₂NO₃ were phase-matchable in the visible and UV region and feature large SHG responsed that are approximately 5, 5.5, and 5.6 times that of KH₂PO₄ (KDP), respectively. Additionally, these title compounds had wide transparent regions from UV to near IR and larger birefringence, suggesting that these crystals were promising UV NLO materials. And their electronic structures and optical properties were calculated based on DFT methods

Structural Modulation of Nitrate Group with Cations to Affect SHG Responses in RE(OH)₂NO₃ (RE = La, Y, and Gd): New Polar Materials with Large NLO Effect after Adjusting pH Values of Reaction Systems

A series of rare-earth hydroxide nitrate crystals (La­(OH)₂NO₃, Y­(OH)₂NO₃, and Gd­(OH)₂NO₃) have been synthesized through adjusting pH values of reaction systems under the subcritical hydrothermal condition. All the titled compounds were isostructural with the noncentrosymmetric space group P2₁ (No. 4) with layer structure, containing [REO₉] (RE = La,Y, and Gd) polyhedra in each layer. The polyhedra were stacked on top of each other and further connected with zigzag strings of edge sharing to form infinite corrugated sheets that parallel to the a–c plane. The [NO₃] groups that presented two different orientation (A and B) project into the space between the layers. In this study, the angle θ between two different orientation [NO₃] groups was defined. With the decrease of ionic radii from La³⁺, Gd³⁺ to Y³⁺, the θ was increased, which led to different second harmonic generation (SHG) effects on lanthanide hydroxide nitrates. The powder SHG measurements revealed that La­(OH)₂NO₃, Gd­(OH)₂NO₃, and Y­(OH)₂NO₃ were phase-matchable in the visible and UV region and feature large SHG responsed that are approximately 5, 5.5, and 5.6 times that of KH₂PO₄ (KDP), respectively. Additionally, these title compounds had wide transparent regions from UV to near IR and larger birefringence, suggesting that these crystals were promising UV NLO materials. And their electronic structures and optical properties were calculated based on DFT methods

Rational Design of the First Lead/Tin Fluorooxoborates MB₂O₃F₂ (M = Pb, Sn), Containing Flexible Two-Dimensional [B₆O₁₂F₆]_∞ Single Layers with Widely Divergent Second Harmonic Generation Effects

Molecular engineering design is a productive atomic-scale strategy to optimize crystal structure and develop new functional materials. Herein, the first lead/tin fluorooxoborates, MB₂O₃F₂ (M = Pb, Sn), were rationally designed by employing the nonlinear optical crystal Sr₂Be₂B₂O₇ (SBBO) as a parent model. Compared with the rigid [Be₆B₆O₁₅]_∞ double layers in SBBO, MB₂O₃F₂ have flexible two-dimensional [B₆O₁₂F₆]_∞ single layer, which not only keeps the NLO-favorable layered structure but also overcomes the structural instability issues of SBBO. Both compounds exhibited desired short UV cutoff edge. Interestingly, MB₂O₃F₂ exhibit widely divergent second harmonic responses, although they are isostructural and both contain stereochemically active lone-pair cations. Our first-principles calculations revealed that the SHG difference is mainly attributed to the different anisotropies of Pb and Sn SHG-active orbitals, which make constructive and destructive contributions to the SHG effects in PbB₂O₃F₂ and SnB₂O₃F₂, respectively

Molecular Engineering as an Approach To Design a New Beryllium-Free Fluoride Carbonate as a Deep-Ultraviolet Nonlinear Optical Material

It is a great challenge to explore deep-ultraviolet (deep-UV) nonlinear optical (NLO) materials that can achieve a subtle balance among large nonlinear coefficients, moderate birefringence, and deep-ultraviolet (UV) transparency. A new beryllium-free fluoride carbonate Ca₂Na₃(CO₃)₃F was successfully synthesized through molecular engineering design, and large single crystals were grown by spontaneous crystallization with molten fluxes. The substitution of NLO-active [BO₃] groups for [CO₃] groups resulted in an optimal balance among the SHG coefficient, birefringence, and UV transparency. Via comparison of these two iso-structural compounds, the second-harmonic generation coefficients and birefringence of Ca₂Na₃(CO₃)₃F have been greatly improved. Remarkably, Ca₂Na₃(CO₃)₃F exhibited a wide transparent region with a deep-UV absorption edge at 190 nm. These results demonstrated Ca₂Na₃(CO₃)₃F is a promising NLO material in the UV or deep-UV region

Rational Design of the First Lead/Tin Fluorooxoborates MB₂O₃F₂ (M = Pb, Sn), Containing Flexible Two-Dimensional [B₆O₁₂F₆]_∞ Single Layers with Widely Divergent Second Harmonic Generation Effects

Molecular engineering design is a productive atomic-scale strategy to optimize crystal structure and develop new functional materials. Herein, the first lead/tin fluorooxoborates, MB₂O₃F₂ (M = Pb, Sn), were rationally designed by employing the nonlinear optical crystal Sr₂Be₂B₂O₇ (SBBO) as a parent model. Compared with the rigid [Be₆B₆O₁₅]_∞ double layers in SBBO, MB₂O₃F₂ have flexible two-dimensional [B₆O₁₂F₆]_∞ single layer, which not only keeps the NLO-favorable layered structure but also overcomes the structural instability issues of SBBO. Both compounds exhibited desired short UV cutoff edge. Interestingly, MB₂O₃F₂ exhibit widely divergent second harmonic responses, although they are isostructural and both contain stereochemically active lone-pair cations. Our first-principles calculations revealed that the SHG difference is mainly attributed to the different anisotropies of Pb and Sn SHG-active orbitals, which make constructive and destructive contributions to the SHG effects in PbB₂O₃F₂ and SnB₂O₃F₂, respectively

Rational Design of the First Lead/Tin Fluorooxoborates MB₂O₃F₂ (M = Pb, Sn), Containing Flexible Two-Dimensional [B₆O₁₂F₆]_∞ Single Layers with Widely Divergent Second Harmonic Generation Effects

Molecular engineering design is a productive atomic-scale strategy to optimize crystal structure and develop new functional materials. Herein, the first lead/tin fluorooxoborates, MB₂O₃F₂ (M = Pb, Sn), were rationally designed by employing the nonlinear optical crystal Sr₂Be₂B₂O₇ (SBBO) as a parent model. Compared with the rigid [Be₆B₆O₁₅]_∞ double layers in SBBO, MB₂O₃F₂ have flexible two-dimensional [B₆O₁₂F₆]_∞ single layer, which not only keeps the NLO-favorable layered structure but also overcomes the structural instability issues of SBBO. Both compounds exhibited desired short UV cutoff edge. Interestingly, MB₂O₃F₂ exhibit widely divergent second harmonic responses, although they are isostructural and both contain stereochemically active lone-pair cations. Our first-principles calculations revealed that the SHG difference is mainly attributed to the different anisotropies of Pb and Sn SHG-active orbitals, which make constructive and destructive contributions to the SHG effects in PbB₂O₃F₂ and SnB₂O₃F₂, respectively

M₂B₁₀O₁₄F₆ (M = Ca, Sr): Two Noncentrosymmetric Alkaline Earth Fluorooxoborates as Promising Next-Generation Deep-Ultraviolet Nonlinear Optical Materials

Two novel noncentrosymmetric alkaline earth fluorooxoborates, M₂B₁₀O₁₄F₆ (M = Ca, Sr), were synthesized and characterized. Both of these two isostructural compounds had layered [B₅O₇F₃]_∞ structures with large second harmonic generation (SHG) responses ranging from 2.3 to 2.5 × KH₂PO₄ (KDP) and short UV absorption edges (<200 nm). The first-principles calculation demonstrated that their nonlinear optical (NLO) properties were superior to those of KBe₂BO₃F₂ (KBBF). In contrast to the alkali fluorooxoborates, these two fluorooxoborates showed not only remarkable stability against air and moisture but also high thermal stability. Therefore, M₂B₁₀O₁₄F₆ (M = Ca, Sr) should be promising deep-ultraviolet (DUV) NLO materials

M₂B₁₀O₁₄F₆ (M = Ca, Sr): Two Noncentrosymmetric Alkaline Earth Fluorooxoborates as Promising Next-Generation Deep-Ultraviolet Nonlinear Optical Materials

Two novel noncentrosymmetric alkaline earth fluorooxoborates, M₂B₁₀O₁₄F₆ (M = Ca, Sr), were synthesized and characterized. Both of these two isostructural compounds had layered [B₅O₇F₃]_∞ structures with large second harmonic generation (SHG) responses ranging from 2.3 to 2.5 × KH₂PO₄ (KDP) and short UV absorption edges (<200 nm). The first-principles calculation demonstrated that their nonlinear optical (NLO) properties were superior to those of KBe₂BO₃F₂ (KBBF). In contrast to the alkali fluorooxoborates, these two fluorooxoborates showed not only remarkable stability against air and moisture but also high thermal stability. Therefore, M₂B₁₀O₁₄F₆ (M = Ca, Sr) should be promising deep-ultraviolet (DUV) NLO materials

M₂B₁₀O₁₄F₆ (M = Ca, Sr): Two Noncentrosymmetric Alkaline Earth Fluorooxoborates as Promising Next-Generation Deep-Ultraviolet Nonlinear Optical Materials

Two novel noncentrosymmetric alkaline earth fluorooxoborates, M₂B₁₀O₁₄F₆ (M = Ca, Sr), were synthesized and characterized. Both of these two isostructural compounds had layered [B₅O₇F₃]_∞ structures with large second harmonic generation (SHG) responses ranging from 2.3 to 2.5 × KH₂PO₄ (KDP) and short UV absorption edges (<200 nm). The first-principles calculation demonstrated that their nonlinear optical (NLO) properties were superior to those of KBe₂BO₃F₂ (KBBF). In contrast to the alkali fluorooxoborates, these two fluorooxoborates showed not only remarkable stability against air and moisture but also high thermal stability. Therefore, M₂B₁₀O₁₄F₆ (M = Ca, Sr) should be promising deep-ultraviolet (DUV) NLO materials

Correction to “M₂B₁₀O₁₄F₆ (M = Ca, Sr): Two Noncentrosymmetric Alkaline Earth Fluorooxoborates as Promising Next-Generation Deep-Ultraviolet Nonlinear Optical Materials”

Correction to “M₂B₁₀O₁₄F₆ (M = Ca, Sr): Two Noncentrosymmetric Alkaline Earth Fluorooxoborates as Promising Next-Generation Deep-Ultraviolet Nonlinear Optical Materials