Wei-Long Zhang

A Strong Second-Harmonic Generation Material Cd4BiO(BO3)3 Originating from 3-Chromophore Asymmetric Structures

In this communication, the novel nonlinear optical crystal material Cd(4)BiO(BO(3))(3) with 3-chromophore asymmetric structures of CdO(n), BiO(6), and BO(3) groups has been prepared by a flux method, and the single crystal structure has been determined with the space group Cm. It is the largest NLO coefficient for Cd(4)BiO(BO(3))(3) among borate systems, and the strong NLO response originates from cooperation effects of the 3-chromophore asymmetric structures composed of the polar displacement of d(10) Cd(2+) ion, stereochemically active lone pair of Bi(3+), and pi-delocalization of BO(3). These evidence are provided in view of evaluations of calculated density of states and electron-density difference maps. The experimental measurements show that the features of a large SHG effect, phase-match, and high thermal stability will be favorable in industrial production and applications for Cd(4)BiO(BO(3))(3).

Syntheses and characterization of new mid-infrared transparency compounds: centric Ba2BiGaS5 and acentric Ba2BiInS5.

Two new mid-infrared transparency compounds, centric Ba(2)BiGaS(5) (1) and acentric Ba(2)BiInS(5) (2), were synthesized from a high-temperature solid-state reaction in evacuated closed silica tubes. Their crystal structures were determined by a single crystal X-ray diffraction method at 293 K. The results of crystal structure solution indicate that compound 1 crystallizes in the centrosymmetric space group Pnma with trans- (1)(∞)[BiGaS(5)](4-) chain structure, while compound 2 crystallizes in the noncentrosymmetric polar space group Cmc2(1) with cis- (1)(∞)[BiInS(5)](4-) chain structure. Two types of lone-pair electrons alignment fashions within (1)(∞)[BiMS(5)](4-) chains result in destructive (for 1) or constructive (for 2) dipole moments, as illustrated in the crystal structures and the partial electron density maps based on the first-principles electronic structure computations. Powder second-harmonic generation (SHG) experiments with a 2.05 μm pumping laser show that the SHG efficiency of the polar compound 2 is approximately 0.8 times that of KTiOPO(4) (KTP) reference. Furthermore, SHG signal intensity measurements using different size particles of powder samples indicate that compound 2 can also achieve type I phase-matching, which makes the compound promising for practical applications.

Syntheses, Characterization, and Optical Properties of Ternary Ba–Sn–S System Compounds: Acentric Ba7Sn5S15, Centric BaSn2S5, and Centric Ba6Sn7S20

Three new ternary Ba-Sn-S system compounds, acentric Ba(7)Sn(5)S(15), centric BaSn(2)S(5), and centric Ba(6)Sn(7)S(20) have been designed and synthesized by a conventional high-temperature solid-state reaction method using the evacuated silica tubes. The crystal structure of Ba(7)Sn(5)S(15) shows the coexistence of a SnS(4) tetrahedral and a Sn(2)S(3) trigonal bipyramid. Importantly, the larger dipole moment of the [Sn(2)S(3)](2-) trigonal bipyramid group and the polarity enhancement of the bipyramidal arrangements result in a strong SHG effect at 2.05 μm, which is 10 times of the SHG intensity of the benchmark AgGaS(2) with the particle size of 30-46 μm and twice as much as that with the particle size of 150-212 μm. Evidently, the acentric Ba(7)Sn(5)S(15) is a novel IR NLO crystal material with a wide mid-IR window and a strong SHG effect, which is the first reported among the Ba-Sn-S ternary system. Moreover, Ba(7)Sn(5)S(15) can achieve type-I phase-matching that can be used for practical applications. In the centric BaSn(2)S(5,) all Sn atoms are coordinated by five S atoms to form novel SnS(5) trigonal bipyramid polyhedrons. In the other centric Ba(6)Sn(7)S(20), there is the coexistence of the two coordination patterns with a SnS(5) trigonal bipyramid and SnS(4) tetrahedral polyhedrons, featuring a special crystal structure in the Ba-Sn-S system.

Syntheses and Characterizations of Cs2Cr3(BP4O14)(P4O13) and CsFe(BP3O11) Compounds with Novel Borophosphate Anionic Partial Structures

Explorations of the A(I)-M(III)-B(III)-P(V)-O quinary system under solid-state reactions led to an anhydrous cesium-chromium borophosphate-phosphate and an anhydrous cesium-iron borophosphate, namely, Cs(2)Cr(3)(BP(4)O(14))(P(4)O(13)) (1) and CsFe(BP(3)O(11)) (2). They both feature complicated three-dimensional (3D) frameworks and represent the first examples of borophosphate frameworks with a P-O-P connection. Compound 1 contains a novel anionic borophosphate partial structure [B(P(2)O(7))(2)](5-) with B:P = 1:4 besides an isolated [P(4)O(13)](6-) anion. Its 3D structure is composed of a layer of [CrB(P(2)O(7))(2)](n)(2n-) and a neutral layer of [Cr(2)(P(4)O(13))](n) interconnected with the linking of P-O-Cr, and the Cs ions are located at the space. Compound 2 contains another novel borophosphate anionic unit of [B(PO(4))(P(2)O(7))](4-) with B:P = 1:3, which further bridges the Fe cations to constitute the whole structure. Both compounds are of high thermal stable and transparent in the range of 0.75-7.1 microm. Magnetic measurements indicate that there exist antiferromagnetic interactions in both compounds.

Syntheses and magnetic properties study of isostructural BiM2BP2O10 (M = Co, Ni) containing a quasi-1D linear chain structure.

We present here the structures and magnetism of two quasi-1D linear chain compounds of BiM(2)BP(2)O(10) (M = Co, Ni), which were synthesized by traditional solid-state reactions for the first time. Two title compounds crystallize in the monoclinic system with space group P2(1)/c and feature novel 3D structures with a linear chain structure of {MO(6)}(n) further connected by [BP(2)O(10)](7-) anionic groups. The results of magnetic property measurements evidence the antiferromagnetic properties of both compounds in low magnetic field and a field-dependent metamagnetic transition from the antiferromagnetic to ferromagnetic ground state of the BiCo(2)BP(2)O(10) complex.

Syntheses, Crystal and Electronic Structures, and Characterizations of Quaternary Antiferromagnetic Sulfides: Ba2MFeS5 (M = Sb, Bi)

Two new quaternary sulfides, Ba(2)SbFeS(5) and Ba(2)BiFeS(5), were synthesized by using a conventional high-temperature solid-state reaction method in closed silica tubes at 1123 K. The two compounds both crystallize in the orthorhombic space group Pnma with a = 12.128(6) Å, b = 8.852(4) Å, c = 8.917(4) Å, and Z = 4 for Ba(2)SbFeS(5) and a = 12.121(5) Å, b = 8.913(4) Å, c = 8.837(4) Å, and Z = 4 for Ba(2)BiFeS(5). The crystal structure unit can be viewed as an infinite one-dimensional edge-shared MS(5) (M = Sb, Bi) tetragonal-pyramid chain with FeS(4) tetrahedra alternately arranged on two sides of the MS(5) polyhedral chain via edge-sharing (so the chain can also be written as (1)(∞)[MFeS(5)](4-)). Interestingly, the compounds have the structural type of a Ba(3)FeS(5) high-pressure phase considering one Ba(2+) is replaced by one Sb(3+)/Bi(3+), with Fe(4+) reduced to Fe(3+) for in order to maintain the electroneutrality of the system. As a result, the isolated iron ions in Ba(3)FeS(5) are bridged by intermediate MS polyhedra in Ba(2)MFeS(5) (M = Sb, Bi) compounds and form the (1)(∞)[MFeS(5)](4-) chain structure. This atom substitution of Ba(2+) by one Sb(3+)/Bi(3+) leads to a magnetic transition from paramagnetic Ba(3)FeS(5) to antiferromagnetic Ba(2)MFeS(5), resulting from an electron-exchange interaction of the iron ions between inter- or intrachains. Magnetic property measurements indicate that the two compounds are both antiferromagnetic materials with Néel temperatures of 13 and 35 K for Ba(2)SbFeS(5) and Ba(2)BiFeS(5), respectively. First-principles electronic structure calculations based on density functional theory show that the two compounds are both indirect-band semiconductors with band gaps of 0.93 and 1.22 eV for Ba(2)SbFeS(5) and Ba(2)BiFeS(5), respectively.

Synthesis and Magnetic Properties of a New Borophosphate SrCo2BPO7 with a Four-Column Ribbon Structure

A new borophosphate SrCo2BPO7 is synthesized by a conventional high-temperature solid-state reaction. The titled compound is found to crystallize in monoclinic system with space group P21/c, which displays a distorted four-column ribbon structure. Both BO3 triangles and PO4 tetrahedra are isolated, while irregular triangles built by Co(2+) ions are found to exist between the connecting ribbons. Magnetic behaviors are investigated by means of susceptibility, magnetization, and heat capacity measurements. The results confirm that SrCo2BPO7 possesses a three-dimensional antiferromagnetic ordering at 25 K. The possible spin arrangements in the system are also suggested.

BaM(BS3)S (M = Sb, Bi): Two New Thioborate Compounds with One-Dimensional Polymeric Chain Structure

Two new quaternary thioborate compounds with strongly one-dimensional growth, BaSb(BS(3))S and BaBi(BS(3))S, have been synthesized using the conventional solid state reaction method in closed tubes at 1100 K. The single crystal X-ray diffraction analysis has shown that compound BaSb(BS(3))S crystallizes in space group Pnma of the orthorhombic system with unit cell parameters of a = 9.6898(15) A, b = 6.2293(13) A, c = 11.670(2) A, V = 704.4(2) A(3), and Z = 4, while compound BaBi(BS(3))S crystallizes in space group C2/m with unit cell parameters of a = 14.9890(17) A, b = 6.2457(6) A, c = 7.5591(9) A, beta = 101.604(5) degrees , V = 693.19(13) A(3), and Z = 4. The two compounds both crystallize in the structure of infinite one-dimensional chains with [BS(3)](3-) trigonal plane coordination alternately bridged by [MS(3)](3-) (M = Sb, Bi) trigonal pyramids through sharing two sulfur atoms along the crystallographic b axis. First-principles electronic structure calculations performed with the density functional theory (DFT) method show that the calculated band gaps of BaSb(BS(3))S and BaBi(BS(3))S are 2.29 and 2.16 eV, respectively, which are in good agreement with the experimental values estimated from UV-vis absorption spectra using the Kubelka-Munk equation, and the observed absorption peak is assigned as charge transfers from S-3p states to Sb-5p (Bi6p) states.

Design of SHG materials with mid-infrared transparency based on genetic engineering for Ba2BiInA5 (A = Se, Te)

We have employed genetic engineering through a four-step roadmap to design second-harmonic generation materials with infrared transparency. Firstly, we constructed virtual crystals of Ba2BiInA5 (A = Se, Te) using the “genome” BiA5 pyramid and InA4 tetrahedron. We then carried out reliable predictions of the crystal structures and revealed the asymmetric central group of these crystal compounds. Thirdly we carried out ab initio computations of the band structures and simulations of the optical properties. We surveyed the nonlinear optical figure of merit for the optical transparent range and the SHG parameters for these crystals. Finally, we provide evidence for the predictions by experimental synthesis, crystal structural determinations and optical measurements for the Ba2BiInSe5 compound.

Long-range and short-range orderings in K4Fe4P5O20 with a natrolite-like framework

K4Fe4P5O20 shows an interesting natrolite-like structure with a spin-tetrahedron lattice built by mixed valence Fe ions. Single crystals of the title compound are successfully grown by the flux method using KF as flux. Magnetic results combined from magnetic, heat capacity, and (57)Fe Mössbauer spectra measurements show that K4Fe4P5O20 possesses a short-range magnetic ordering at ∼13 K and a long-range ordering at ∼7 K. Magnetic anisotropy of K4Fe4P5O20 is observed between H‖c and H⊥c, suggesting that the c-axis is the magnetic easy-axis. The spin arrangements in the system are suggested to be ferrimagnetic along the natrolite chains.