Lei Geng

Huaibei Normal University, Hua-pei-ts’un, Shanxi Sheng, China

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Publications (13)40.11 Total impact

  • [Show abstract] [Hide abstract]
    ABSTRACT: A new ternary sulfide Ba3Sb2S7 was synthesized from high temperature solid-state reactions in a flame-sealed silica ampoule. It crystallizes in the C2/c space group of the monoclinic system with a = 18.380(2) Å, b = 12.266(2) Å, c = 13.164(2) Å, β = 110.054(6)°, V = 2788.0(7) Å3, and Z = 8. The compound features an interesting zero-dimensional structure built of two types of isolated SbS3 and SbS2(S2) units surrounded with the charge balanced Ba2+ cations. The UV-Vis-NIR optical diffuse reflectance measurements along with the electronic band structure calculations indicate that Ba3Sb2S7 belongs to an indirect semiconductor with the band gap of 2.4 eV. Electronic density of states (DOS) analyses were also performed to interpret the intrinsic behavior of charge transfers in the SbS3 and SbS2(S2) units, respectively.
    Journal of Molecular Structure 09/2013; · 1.40 Impact Factor
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    ABSTRACT: A new strontium antimonateIII, Sr5Sb22O38, has been hydrothermally synthesized and structurally characterized by single crystal X-ray diffraction. It crystallizes in the P21/n space group of the monoclinic system with a=11.739(9) Å, b=12.014(10) Å, c=16.412(13) Å, β=91.460(8)°, V=2314.0(3) Å3. The crystal structure is built of seven trigonal–pyramidal SbO3 and four sphenoid SbO4 polyhedra which are connected through sharing corner-oxygen atoms to form the complex three-dimensional ∞3[Sb22O38]10− anionic network with two different intersectant tunnels along the [111̄] and [11̄1̄] directions accommodating the electric charge balanced Sr2+ cations. First-principles electronic structure calculations based on the density functional theory (DFT) and the UV–vis diffuse reflectance spectroscopy measurements both indicate that the compound belongs to a direct band insulator with an optical gap value of 3.3 eV.
    Journal of Solid State Chemistry 07/2013; 203:74–78. · 2.04 Impact Factor
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    ABSTRACT: 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.
    Inorganic Chemistry 06/2011; 50(12):5679-86. · 4.59 Impact Factor
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    ABSTRACT: The structural, optical, and electronic properties of four rare-earth bismuth tungstate compounds, LnBiW(2)O(9) (Ln = Ce, Sm, Eu, Er), have been investigated by means of single-crystal X-ray diffraction, elemental analyses, and spectral measurements. For some of the compounds, the calculations of energy band structures and density of states have also been made by the density functional theory. The structure of CeBiW(2)O(9) features a three-dimensional (BiW(2)O(9))(3-) anionic framework with interesting channels where Ce atoms are located. The framework is constructed by one-dimensional BiO(9) polyhedra chains and one-dimensional zigzag W(2)O(9) chains via edge- and face-sharing. LnBiW(2)O(9) (Ln = Sm, Eu, Er) are isostructural and their structures feature a three-dimensional network based on alternating (BiO(2))(-) layers and (Ln(2)W(2)O(12))(6-) layers connected by corner-linked chains of WO(6) octahedra. Results of spectral measurements indicate that EuBiW(2)O(9) exhibit the characteristic yellow-red light emission under excitation at 395 nm, and it will be a red phosphor in designing white light-emitting diode device. The calculated results of band structures by using the density functional theory (DFT) show that the solid-state compound CeBiW(2)O(9) and SmBiW(2)O(9) are indirect band gap materials.
    Dalton Transactions 06/2011; 40(28):7357-64. · 3.81 Impact Factor
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    ABSTRACT: Two new quaternary thioborates, PbSbBS(4) and PbBiBS(4), have been synthesized from solid-state reaction methods at temperatures from 1073 to 1123 K in evacuated sealed quartz tubes. The crystal structures have been determined by means of single crystal X-ray diffraction and they both crystallize in the P2(1)/m space group of the monoclinic system with a = 5.9532(18) Å, b = 6.2031(13) Å, c = 9.250(3) Å, β = 108.200(16)°, Z = 2 for PbSbBS(4) and a = 5.971(10) Å, b = 6.273(9) Å, c = 9.132(15) Å, β = 107.75(2)°, Z = 2 for PbBiBS(4), respectively. The two compounds are isostructural and both constructed with the infinite one-dimensional [MBS(4)](2-) (M = Sb or Bi) chains as building blocks, which are composed of [BS(3)](3-) trigonal plane units with [MS(3)](3-) (M = Sb or Bi) trigonal pyramids connected alternatively through corner-sharing along the crystallographic b axis. Two adjacent [MBS(4)](2-) chains are further bridged by the intermediate Pb(2+) cations, forming a novel S-shaped Pb-[MBS(4)] dimeric chain structure. In addition, first-principles electronic structure calculations based on the density functional theory (DFT) were performed on compound PbSbBS(4), indicating that the compound belongs to direct semiconductor with a band gap of 1.803 eV, which is in good agreement with the experimental value estimated from the UV-Vis diffuse reflectance spectroscopy.
    Dalton Transactions 03/2011; 40(17):4474-9. · 3.81 Impact Factor
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    ABSTRACT: 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.
    Inorganic Chemistry 02/2011; 50(6):2378-84. · 4.59 Impact Factor
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    ABSTRACT: The title compounds are prepared by solid state reactions of BaS, Bi (or Sb), B, and S in the molar ratios of 1:1:1:3 (graphite crucibles, 1100 K, 10 h) and characterized by single crystal XRD, UV/VIS spectroscopy, and DFT electronic structure calculations.
    ChemInform 09/2010; 41(39).
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    ABSTRACT: The title compounds are obtained quantitatively by reacting mixtures of M2O3 (M: Fe, In), H3BO3, and NH4H2PO4 in a molar ratio of 1:1:3 at 1153 K.
    ChemInform 08/2010; 41(34).
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    ABSTRACT: 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.
    Inorganic Chemistry 07/2010; 49(14):6609-15. · 4.59 Impact Factor
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    ABSTRACT: 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.
    Inorganic Chemistry 03/2010; 49(5):2550-6. · 4.59 Impact Factor
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    ABSTRACT: 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).
    Journal of the American Chemical Society 02/2010; 132(5):1508-9. · 10.68 Impact Factor
  • ChemInform 01/2010; 41(22).
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    ABSTRACT: ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.
    ChemInform 01/2010; 41(28).

Publication Stats

27 Citations
40.11 Total Impact Points

Institutions

  • 2013
    • Huaibei Normal University
      Hua-pei-ts’un, Shanxi Sheng, China
  • 2010–2011
    • Northeast Institute of Geography and Agroecology
      • State Key Laboratory of Structural Chemistry
      Beijing, Beijing Shi, China