New Fluoride Carbonates: Centrosymmetric KPb2(CO3)2F and Noncentrosymmetric K2.70Pb5.15(CO3)5F3

Noncentrosymmetric Crystal [C10H8NO2]2SiF6·H2O with Large Birefringence

Crystals with noncentrosymmetric structures are applied in many fields, but reported compounds have a high probability of forming a centrosymmetric structure. Here, by hydrogen-bonding the π-conjugated [C10H8NO2]+ cation with the separated [SiF6]2- octahedron, a noncentrosymmetric isoquinoline hexafluorosilicate monohydrate optical crystal of [C10H8NO2]2SiF6·H2O was formed under the regulatory influence of hydrogen bonding. It not only possesses a moderate second harmonic generation response (1.0 × KDP) but also has a large birefringence (0.282 at 550 nm), which is greater than those of most commercial birefringent crystals. In addition, the UV-vis-NIR diffuse reflectance spectrum and thermal stability analysis are also reported. Our finding gives insight into how to design noncentrosymmetric structural compounds in the organic-inorganic system.

K2Pb(H2C3N3O3)4(H2O)4: a potential UV nonlinear optical material with large birefringence

K₂Pb(H₂C₃N₃O₃)₄(H₂O)₄ (I) features a 2D [K₂PbO₈(H₂O)₄]^12- anionic layer and reveals a moderate SHG signal of approximately 2.6 × KDP.

Two alkali calcium borates exhibiting second harmonic generation and deep-UV cutoff edges

KCa₄B₃O₉ and K_0.59Rb_0.41Ca₄B₃O₉ crystallize in the polar space group with moderate SHG responses. Calculations were performed to elucidate the structure–property relationships.

Structural modulation induced by MIIIA metals in Ba3MQ4X (M = Al, Ga, In; Q = S, Se; X = Cl, Br): an experimental and computational analysis

The optical properties of Ba₃MQ₄X (M = Al, Ga, In; Q = S, Se; X = Cl, Br) have been studied and their structures have been compared.

Na4Yb(CO3)3F: A New UV Nonlinear Optical Material with a Large Second Harmonic Generation Response

A new nonlinear optical crystals fluoride carbonate, Na4Yb(CO3)3F, has been synthesized by mild hydrothermal method. The Na4Yb(CO3)3F crystallizes in the noncentrosymmetric space group Cc (no. 9) with the lattice parameters a = 8.018(3), b = 15.929(5), c = 13.950(5) Å and β = 101.425(6)°. The compound Na4Yb(CO3)3F has a high density of [CO3] groups. The structure can be described as one-dimensional [Na5Yb(CO3)2F2] chains connected by [CO3] groups, forming an intricate three-dimensional (3D) framework. Other Na+ and Yb3+ cations are located in the cavities of 3D network. The powder second harmonic generation (SHG) measurement shows that Na4Yb(CO3)3F features a large SHG response, about 4.3 times that of KH2PO4 (KDP), and is a phase-matchable material. In addition, its UV-Vis-NIR diffuse reflectance spectral data indicate that Na4Yb(CO3)3F has a large optical gap about 4.72 eV, which corresponds to the UV cut-off edge of 263 nm.

Hydrocerussite-related minerals and materials: structural principles, chemical variations and infrared spectroscopy

White lead or basic lead carbonate, 2PbCO3·Pb(OH)2, the synthetic analogue of hydrocerussite Pb3(OH)2(CO3)2, has been known since antiquity as the most frequently used white paint. A number of different minerals and synthetic materials compositionally and structurally related to hydrocerussite have been described within the last two decades. Herein, a review is given of general structural principles, chemical variations and IR spectra of the rapidly growing family of hydrocerussite-related minerals and synthetic materials. Only structures containing a hydroxo- and/or oxo-component,i.e.which are compositionally directly related with hydrocerussite and `white lead', are reviewed in detail. An essential structural feature of all the considered phases is the presence of electroneutral [PbCO3]0cerussite-type layers or sheets. Various interleaved sheets can be incorporated between the cerussite-type sheets. Different sheets are stacked into two-dimensional blocks separated by the stereochemically active 6s2lone electron pairs on Pb2+cations. Minerals and synthetic materials described herein, together with a number of still hypothetical members, constitute a family of modular structures. Hydrocerussite, abellaite and grootfonteinite can be considered to constitute a merotype family of structures. The remaining hydrocerussite-related structures discussed are built on similar principles, but are more complex. Structural architectures of somersetite and slag phase from Lavrion, Attica, Greece, are unique for oxysalt mineral structures in general. Thus, the whole family of hydrocerussite-related phases can be denoted as a plesiotype family of modular structures. The crystal structures of hydrocerussite from Merehead quarry, Somerset, England, and of its synthetic analogue, both determined from single crystals, are reported here for the first time. The results of the infrared (IR) spectroscopy show that this method is useful for distinguishing several different minerals related to hydrocerussite and their synthetic analogues.

Role of spin-orbit interaction on the nonlinear optical response of CsPbCO3F using DFT

We explore the effect of spin-orbit interaction (SOI) on the electronic and optical properties of CsPbCO₃F using the full potential linear augmented plane wave method with the density functional theory (DFT) approach. CsPbCO₃F is known for its high powder second harmonic generation (SHG) coefficient (13.4 times (d₃₆ = 0.39 pm V^-1) that of KH₂PO₄ (KDP)). Calculations are done for many exchange correlation (XC) potentials. After the inclusion of SOI, the calculated Tran-Blaha modified Becke-Johnson (TB-mBJ) band gap of 5.58 eV reduces to 4.45 eV in agreement with the experimental value. This is due to the splitting of Pb p-states. Importantly, the occurrence of a band gap along the H-A direction (indirect) transforms to the H-H (direct) high symmetry points/direction in the first Brillouin zone. We noticed a large anisotropy in the calculated complex dielectric function, absorption, and refractive index spectra. The calculated static birefringence of 0.1049 and 0.1057 (with SOI) is found to be higher than that of the other carbonate fluorides. From the Born effective charge (BEC) analysis we notice that the Cs atom shows a negative contribution to birefringence whereas Pb, C, and F atoms show a positive contribution. In addition, we have also calculated the nonlinear optical χ(-2ω;ω,ω) dispersion of a CsPbCO₃F single crystal. We found that d₁₁ = d₁₂ = 4.35 pm V^-1 at 1064 nm, which is 11.2 times higher than d₃₆ of KDP. The origin of the highly nonlinear optical susceptibility dispersion of CsPbCO₃F is explained. Overall, our results are in agreement with experiments and it is obvious from the present study that CsPbCO₃F is a direct band gap, large second harmonic generation, and good phase matchable NLO crystal in the ultraviolet region.

Influence of an oxygen vacancy on the electronic structure of the asymmetric mixed borate–carbonate Pb7O(OH)3(CO3)3(BO3)

The influence of an oxygen vacancy on the electronic properties of a mixed borate–carbonate compound Pb₇O(OH)₃(CO₃)₃(BO₃) is studied.

Synthesis and characterization of CsSrCO3F – a beryllium-free new deep-ultraviolet nonlinear optical material

A noncentrosymmetric fluoride carbonate CsSrCO₃F has been synthesized which is a promising beryllium-free deep-UV nonlinear optical material.

ACdCO3F (A = K and Rb): new noncentrosymmetric materials with remarkably strong second-harmonic generation (SHG) responses enhanced via π-interaction

The remarkably large SHG efficiency of KCdCO₃F originates from enhancement via interatomic interactions between the s and p states of Cd²⁺ and the π-conjugated groups of the [CO₃]²⁻ unit.

Role of acentric displacements on the crystal structure and second-harmonic generating properties of RbPbCO3F and CsPbCO3F

Two lead fluorocarbonates, RbPbCO3F and CsPbCO3F, were synthesized and characterized. The materials were synthesized through solvothermal and conventional solid-state techniques. RbPbCO3F and CsPbCO3F were structurally characterized by single-crystal X-ray diffraction and exhibit three-dimensional (3D) crystal structures consisting of corner-shared PbO6F2 polyhedra. For RbPbCO3F, infrared and ultraviolet-visible spectroscopy and thermogravimetric and differential thermal analysis measurements were performed. RbPbCO3F is a new noncentrosymmetric material and crystallizes in the achiral and nonpolar space group P6m2 (crystal class 6m2). Powder second-harmonic generation (SHG) measurements on RbPbCO3F and CsPbCO3F using 1064 nm radiation revealed an SHG efficiency of approximately 250 and 300 × α-SiO2, respectively. Charge constants d33 of approximately 72 and 94 pm/V were obtained for RbPbCO3F and CsPbCO3F, respectively, through converse piezoelectric measurements. Electronic structure calculations indicate that the nonlinear optical response originates from the distorted PbO6F2 polyhedra, because of the even-odd parity mixing of the O 2p states with the nearly spherically symmetric 6s electrons of Pb(2+). The degree of inversion symmetry breaking is quantified using a mode-polarization vector analysis and is correlated with cation size mismatch, from which it is possible to deduce the acentric properties of 3D alkali-metal fluorocarbonates.

Series of lead oxide hydroxide nitrates obtained by adjusting the pH values of the reaction systems

A series of lead(II) nitrates have been synthesized by a hydrothermal method and adjusting the pH values of the reaction systems. Pb20O6(OH)16(NO3)12 and Pb2O(OH)NO3, crystallize in the centrosymmetric space group P1̅ and Pbca, respectively. The structure of Pb20O6(OH)16(NO3)12 features infinite cationic chains of [Pb20O6(OH)16]∞ running along c axis, and the nitrate groups as the counterions reside between adjacent chains, while the structure of Pb2O(OH)NO3 can be described as alternate stacking of cationic [Pb2O(OH)]∞ layers with anionic [NO3](-) layers along [001] direction by the weak Pb-O bonds, forming a 3D framework with 1D tunnels of 12-member rings (MRs). [Pb4(OH)4](NO3)4, crystallizing in the noncentrosymmetric space group Cc, has been studied as the nonlinear optical material for the first time. The second harmonic generation (SHG) measurement indicates that the SHG responses of [Pb4(OH)4](NO3)4 are 0.7 times that of KDP. Theoretical calculations confirmed the SHG efficiency of [Pb4(OH)4](NO3)4 originates from the cooperative effect of NO3(-) groups and lead oxygen polyhedras in the structure. Meanwhile, the relationship between pH value and ratio of Pb/OH(-) in the molecules presents a positive correlation, which results in the diversity of these structures under different pH value.

Ba2B10O17: a new centrosymmetric alkaline-earth metal borate with a deep-UV cut-off edge

Ba₂B₁₀O₁₇, a new barium borate, with a band-gap of 5.97 eV, possesses a wide transmission range from 180 to 3000 nm.