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A new chloride borate, Ba 1.31 Sr 3.69 (BO 3 ) 3 Cl, was obtained when exploring potential phosphor materials. It belongs to orthorhombic system, Pnma space group, with cell parameters of a = 6.965(1) Å, b = 16.546(3) Å, c = 9.557(1) Å and Z = 4. Ba 5- x Sr x (BO 3 ) 3 Cl ( x = 0, 0.5, …to 5) was synthesized and the cell volumes of the solid solutions were obtained by Rietveld refinement. Detailed structure description of Ba 1.31 Sr 3.69 (BO 3 ) 3 Cl was conducted and the structure comparison between Ba 1.31 Sr 3.69 (BO 3 ) 3 Cl and M 5 (BO 3 )X (M = Ba or Sr, X = Cl or F) was illustrated. In Ba 1.31 Sr 3.69 (BO 3 ) 3 Cl, there are hexagonal tunnels extending along a -axis, which is the main feature of apatite family compounds. The density functional theory calculation suggested that in Ba 1.31 Sr 3.69 (BO 3 ) 3 Cl space group Pnma is more energy favourable than C 222 1 . DSC-TG showed that Ba 1.31 Sr 3.69 (BO 3 ) 3 Cl is stable up to 950 °C and Raman and Infrared spectroscopy demonstrate the existence of planar (BO 3 ) 3- in the structure. [ABSTRACT FROM AUTHOR]

• Single crystal structure of a novel ultraviolet NLO tourmaline was solved. • Sellmeier equations were obtained by fitting the measured refractive indices. • Phase matching range of the title crystal is obtained from the Sellmeier equations. • The linear and NLO properties were investigated by the experimental and theory calculation. Transparent tourmaline NaAl 9 (BO 3) 3 Si 6 O 21 OH is first reported by combining experimental and theory calculation methods, which exhibits potential ultraviolet nonlinear optical properties. [Display omitted] Tourmaline, as an important mineral, has received intensive interest, since it is not only a valuable gemstone, but also is a piezoelectric or pyroelectric material, due to the polar structural configuration. However, its nonlinear optical (NLO) properties were not explored so far, because a transparent crystal with high transmittance is scarce, being essential to optical functional materials. Here, we report a novel ultraviolet (UV) NLO tourmaline crystal with chemical composition NaAl 9 (BO 3) 3 Si 6 O 21 OH for the first time by combining first-principles analysis and experimental measurements. It exhibits a short UV absorption edge, considerable second harmonic generation effect and moderate birefringence, thereby facilitating its phase-matching coherent beam output in the range from visible to UV regions. [ABSTRACT FROM AUTHOR]

The first two members in the quaternary A/A′/M/Q (A = alkali metal; A′ = alkaline-earth metal; M = As, Sb, Bi; Q = S, Se, Te) system, namely the KBaMSe 3 (M = As, Sb) selenides, have been synthesized by solid state reactions. They are isostructural and crystallize in the centrosymmetric space group P 2 1 / c of the monoclinic system. In the structure, the trivalent M atom (M = As, Sb) is coordinated to three Se atoms forming a trigonal pyramid with the Se atoms serving as the triangle base, showing the stereochemical activity of the ns 2 lone pair electron. The MSe 3 (M = As, Sb) trigonal pyramids are totally isolated from each other with K + and Ba 2+ cations located between them. The optical band gaps of 2.26 (2) eV for KBaAsSe 3 and 2.04 (2) eV for KBaSbSe 3 , were deduced from the diffuse reflectance spectra. The first principles calculations were performed to study the electronic structures of KBaMSe 3 (M = As, Sb) compounds and the results indicated that these two compounds are indirect band gap semiconductors. [ABSTRACT FROM AUTHOR]

Highlights: [•] Three new chalcohalides: Ba4Ge2PbS8Br2, Ba4Ge2PbSe8Br2 and Ba4Ge2SnS8Br2 have been synthesized. [•] The MQ5Br octahedra and GeQ4 tetrahedra form a three-dimensional framework with Ba2+ in the channels. [•] Band Gaps and electronic structures of the three compounds were studied. [ABSTRACT FROM AUTHOR]