Synthesis, structure, and electronic properties of the Li11RbGd4Te6O30 single crystal.

Materials with spin dimers have attracted much attention in the last several decades because they could provide a playground to embody simple quantum spin models. For example, the Bose-Einstein condensation of magnons has been observed in TlCuCl3 with anti-ferromagnetic Cu2Cl6 dimers. In this work, we have synthesized a new kind of single-crystal Li11RbGd4Te6O30 with Gd2O15 dimers. This material belongs to the rhombohedral system with the lattice parameters: a = b = c = 16.0948 Å and α = ß = γ = 33.74°. First-principles calculations indicate that Li11RbGd4Te6O30 is a wide-bandgap (about 4.5 eV) semiconductor. But unlike many other well studied quantum dimer magnets with an anti-ferromagnetic ground state, the Gd2O14 dimers in Li11RbGd4Te6O30 show ferromagnetic intra-dimer exchange interactions according to our calculations. Our work provides a new material which could possibly extend the studies of the spin dimers.

White-Light Emission from a Semi-Conductive Borate-Stannate.

In response to ever-increasing application requirements in lighting and displays, a tremendous emphasis is being placed on single-component white-light emission. Single-component inorganic borates doped with rare earth metal ions have shown prominent achievements in white-light emission. The first environmentally friendly defect-induced white-light emitting crystalline inorganic borate, Ba2 [Sn(OH)6 ][B(OH)4 ]2 , has been prepared. Additionally, it is the first borate-stannate without a Sn-O-B linkage. Notably, Ba2 [Sn(OH)6 ][B(OH)4 ]2 shows Commission Internationale de l'Eclairage (CIE) chromaticity coordinates of (0.42, 0.38), an ultrahigh color rendering index (CRI) of 94.1, and an appropriate correlated color temperature (CCT) of 3083 K. Such a promising material will provide a new approach in the development of white-light emitting applications.

Ba4Bi2(Si8-x B4+x O29) (x = 0.09): a new acentric metal borosilicate as a promising nonlinear optical material.

A new acentric metal borosilicate, namely Ba4Bi2(Si8-x B4+x O29) (x = 0.09), has been synthesized by a standard solid-state reaction. The title compound crystallizes in noncentrosymmetric (NCS) space group I4[combining macron]2m with lattice parameters a = 11.0254(4) Å and c = 10.3961(9) Å. Structure refinements indicate that mixing of B atoms and Si atoms exists for a few atomic sites. In the "ideal" Ba4Bi2(Si8B4O29), BO4 or SiO4 tetrahedra are inter-connected by corner-sharing to cyclic B4O12 or Si4O12 units. These B4O12 and Si4O12 units are further interconnected via corner-sharing to an "ideal" [Si8B4O29]14- 3D network. The Ba2+ and Bi3+ act as the counter cations and are located at the cavities of the structure. Ba4Bi2(Si8-x B4+x O29) (x = 0.09) melts incongruently at a high temperature of 929 °C. Powder second-harmonic generation (SHG) measurements reveal that Ba4Bi2(Si8-x B4+x O29) (x = 0.09) is a type I phase-matching compound with a good SHG response of about 5.1 times that of KDP (KH2PO4), which is the highest among the borosilicates reported so far. The SHG source has been studied by DFT theoretical calculations. Our preliminary results indicate that Ba4Bi2(Si8-x B4+x O29) (x = 0.09) is a new second-order nonlinear-optical crystalline material candidate.

Three Cadmium Tartratoborates with Good Second Harmonic Generation (SHG) or Luminescence Performances.

Three new cadmium(II) tartratoborates, namely, Cd5[(C4H2O6)2B]2(H2O)8·3H2O (1), K2Cd4[(C4H2O6)2B]2(H2O)2 (2), and Li0.92K1.08Cd1.5[(C4H2O6)2B](H2O)2 (3), have been successfully synthesized by the hydrothermal method. Compounds 1-3 belong to centric C2/ c, acentric Pc, and the polar C2, respectively. Through based on the same hybrid borate-tartrate [(C4H2O6)2B]5- anions, they exhibit different structures. The [(C4H2O6)2B]5- anion is composed of two tartrate anions and a B(OH)4- unit. Compound 1 features a novel 3D network formed by 2D {Cd3[(C4H2O6)2B]2(H2O)2}4- anionic layers and [Cd2O10] dimers, forming tunnels of large 14-MRs which are filled by the non-coordination water molecules. Compound 2 has a characteristic 3D network based on {Cd2[(C4H2O6)2B]}- units interlinked via carboxylate groups, forming tunnels of 11-MRs, half of which stuffed with the K+ ions. Compound 3 features 2D {Cd4[(C4H2O6)4B]}3+ layers which are separated by K/Li ions. Luminescent studies suggest that they emit blue light. Compounds 2 and 3 display phase-matchable second harmonic generation signs of about 3.2× and 1.5× KH2PO4, respectively.

A Facile Route to Nonlinear Optical Materials: Three-Site Aliovalent Substitution Involving One Cation and Two Anions.

Two mixed-metal gallium iodate fluorides, namely, α- and ß-Ba2 [GaF4 (IO3 )2 ](IO3 ) (1 and 2), have been designed by the aliovalent substitutions of α- and ß-Ba2 [VO2 F2 (IO3 )2 ](IO3 ) (3 and 4) involving one cationic and two anionic sites. Both 1 and 2 display large second-harmonic generation responses (≈6×KH2 PO4 (KDP)), large energy band gaps (4.61 and 4.35 eV), wide transmittance ranges (≈0.27-12.5 µm), and high relevant laser-induced damage thresholds (29.7× and 28.3×AgGaS2 , respectively), which indicates that 1 and 2 are potential second-order nonlinear optical materials in the ultraviolet to mid-infrared. Our studies propose that three-site aliovalent substitution is a facile route for the discovery of good NLO materials.

Chiroptical Activity from an Achiral Biological Metal-Organic Framework.

Chiroptical activity is observed from an achiral adenine-containing metal-organic framework (MOF) named ZnFDCA. Such a seemingly counterintuitive phenomenon can, in fact, be predicted by the intrinsic crystal symmetry of 4̅2 m point group. Although theoretically allowed, examples of optically active achiral crystals are extremely rare. ZnFDCA is the first reported achiral MOF showing optical activity, as demonstrated by a pair of circular dichroism signals with opposite signs and enhanced intensity. Moreover, simply through adding an amino substituent to adenine, the chiroptical activity, as well as nonlinear optical activity, of the analogous MOF, namely ZnFDCA-NH2, disappears due to diverse packing pattern giving rise to centrosymmetric crystal symmetry.

Li7(TeO3)3F: A Lithium Fluoride Tellurite with Large Second Harmonic Generation Responses and a Short Ultraviolet Cutoff Edge.

Here, the combination of the strong electropositive lithium and the most electronegative fluorine with the TeO3 group afforded the first lithium fluoride tellurite, namely, Li7(TeO3)3F (P63), which was synthesized by solid-state reactions. Its structure features a novel three-dimensional anionic framework of [Li7O9F]12- composed of LiO3F and LiO4 tetrahedra with one-dimensional hexagonal tunnels of 12-membered rings along the c-axis, filled by the "isolated" ψ-TeO3 tetrahedra. Notably, this compound displays the largest band gap of 4.75 eV among all of the non-centrosymmetric metal-tellurites reported so far, as well as strong second harmonic generation (SHG) responses (3 × KH2PO4 @1064 nm, 0.2 × ß-BaB2O4 @532 nm) and a large laser damage threshold (73 × AgGaS2). Furthermore, theoretical calculations reveal that the LiO4 and LiO3F tetrahedra also contribute significantly to the SHG response (∼30%).

AgGa2 PS6 : A New Mid-Infrared Nonlinear Optical Material with a High Laser Damage Threshold and a Large Second Harmonic Generation Response.

To develop new mid-infrared (MIR) nonlinear optical (NLO) materials, which can overcome the low laser damage threshold (LDT) of the commercial MIR-NLO crystals (AgGaS2 , AgGaSe2 and ZnGeP2 ) and simultaneously keep the large NLO susceptibility, is necessary for high-power MIR laser frequency conversion technology. To improve the LDT, a new strategy of increasing lattice stability was adopted. Here, the strongly covalent structural unit of the PS4 tetrahedron was introduced into AgGaS2 (AGS), and that led to the isolation of the first compound in AgI -GaIII -PV -S system, namely, AgGa2 PS6 (Cc). It retains a large SHG efficiency (1.0×AGS) with phase-matchable ability, and also exhibits an improved LDT (5.1×AGS), indicating AgGa2 PS6 is a new promising MIR-NLO crystal. Moreover, a novel 3D framework of [Ga2 PS6 ]- , with triangular-shaped channels, as well as interesting single triangular geometry of AgS3 -both of which are very rare in reported sulfides-was discovered in AgGa2 PS6 . Furthermore, theoretical calculations, and lattice energy and thermal expansions analyses suggest that the PS4 group makes a large contribution to the large SHG efficiency and high LDT.

Na2RE2TeO4(BO3)2 (RE = Y, Dy-Lu): luminescent and structural studies on a series of mixed metal borotellurates.

The first examples of metal borotellurates, namely, Na2RE2TeO4(BO3)2 (RE = Y, Dy-Lu) have been prepared by using solid-state reactions. They possess similar structures and crystallize in space group P21/c (No. 14). These compounds feature a novel [RE2TeO4(BO3)2](2-) 3D network structure composed of linear [TeO4(BO3)2](8-) anions interconnected by RE(3+) ions with the voids of the network filled by the Na(+) ions. They exhibit high thermal stability (higher than 800 °C). Results of magnetic measurements on Dy, Ho, and Er compounds indicate that they display weak antiferromagnetic interaction between RE(III) centers. Luminescent studies show that Na2Er2TeO4(BO3)2 has a strong emission at 1.562 µm with a wide fwhm (70 nm) and moderate lifetime (0.18 ms), whereas Na2Yb2TeO4(BO3)2 has a strong NIR region emission around 1.02 µm. Furthermore, UV-vis-NIR absorption spectra, infrared spectra, and DFT calculations for the Y compound as a representative were also accomplished.