Wendan Cheng

Chinese Academy of Sciences, Peping, Beijing, China

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Publications (32)83.78 Total impact

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    ABSTRACT: Two nonlinear optical crystal carbonates (Na4La2(CO3)5 and CsNa5Ca5(CO3)8 were successfully synthesized by hydrothermal method, and both of them crystallized in the same noncentrosymmetric hexagonal space group P63mc (No. 186). The structure of Na4La2(CO3)5 consists of a three-dimensional network made up of [CO3] triangles as well as irregular [Na0.67La0.33O10] and [NaO8] polyhedra. The structure of CsNa5Ca5(CO3)8 can be described as the standing-on-edge [CO3] groups connect the adjacent infinite [CaCO3]∞ layers in the ab plane to construct a framework with four types of channels running parallel to [010]. The Na, Cs, and [Na0.67Ca0.33] atoms reside in these channels. The measurement of second harmonic generation (SHG) by the method adapted from Kurtz and Perry indicated that Na4La2(CO3)5 and CsNa5Ca5(CO3)8 were phase-matchable in the visible region and exhibited SHG responses of approximately 3 and 1 × KH2PO4 (KDP). Meanwhile, they exhibited wide transparent region with short UV cutoff edge at about 235 and 210 nm, respectively, suggesting that these crystals as NLO materials may have potential applications in the UV region.
    Inorganic chemistry. 07/2014;
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    ABSTRACT: 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.
    Inorganic Chemistry 05/2014; · 4.59 Impact Factor
  • Zhangzhen He, Wendan Cheng
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    ABSTRACT: Magnetic phase diagram of α-CoV2O6.
    Journal of Magnetism and Magnetic Materials 01/2014; 362:27–30. · 1.83 Impact Factor
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    ABSTRACT: Magnetic anisotropy is confirmed for the first time using a single crystal sample of α-Li3Fe2(PO4)3 obtained by the flux method.
    Journal of Solid State Chemistry. 01/2014; 215:189–192.
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    ABSTRACT: The interfacial magnetoelectric effect and the critical thickness for the ferroelectric in half-metallic ferromagnet/ferroelectric Co2FeSi/BaTiO3 multiferroic tunnel junctions are investigated using a first-principles density-functional theory. The magnetoelectric effect is derived from the difference of the magnetic moments on interfacial atoms, which are sensitive to the polarization of ferroelectric layers in multiferroic tunnel junctions. Besides this, the coupling is found to be dependent on the interfacial electronic hybridizations and to be affected by the choice of the atomic termination. In addition, the magnetoelectric coefficients calculated for the FeSi/TiO2 and Co2/TiO2 interfaces of the junctions are different from each other. Meanwhile, the critical thickness of ferroelectric state was found to be about 1.7 nm in the Co2/TiO2 interface but vanished in the FeSi/TiO2 interface. The half-metallic ferromagnetic/ferroelectric tunnel junctions may open a promising avenue for designing novel electronic and spintronic devices at nanoscale.
    Modelling and Simulation in Materials Science and Engineering 12/2013; 22(1). · 1.93 Impact Factor
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    ABSTRACT: Two nonlinear optical fluoride carbonate crystals (Na8Lu2(CO3)6F2 and Na3Lu(CO3)2F2) have been synthesized under subcritical hydrothermal condition. Both crystals crystallize in the noncentrosymmetric space group Cc (No. 9). The structure of Na8Lu2(CO3)6F2 with high density of [CO3] groups is described as 1D [Na5Lu(CO3)2F2] chains connected by [CO3] triangles, forming an intricate three-dimensional framework. Lu3+ and Na+ cations are alternatively ordered and disordered in the cavities of the 3D network. The structure of Na3Lu(CO3)2F2 is built up from the [NaLu(CO3)2F2] layers which are separated by other Na+ cations. The [CO3] anionic groups arrange approximately coparallel to the plane. The second harmonic generation (SHG) measurement indicates that Na8Lu2(CO3)6F2 and Na3Lu(CO3)2F2 have large SHG responses that are approximately 4.29 and 4.21 times KH2PO4 (KDP), respectively. The responses are also phase-matchable in the visible region. In addition, it exhibits wide transparent regions ranging from UV to near IR with a short UV cutoff edge (<200 nm), which suggests that the new compounds are promising as deep-UV NLO materials.
    ChemInform 07/2013; 25(15):3147–3153.
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    ABSTRACT: A new borophosphate SrCoBPO is synthesized by a conventional high-temperature solid-state reaction. The titled compound is found to crystallize in monoclinic system with space group P2/c, which displays a distorted four-column ribbon structure. Both BO triangles and PO tetrahedra are isolated, while irregular triangles built by Co 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 SrCoBPO possesses a three-dimensional antiferromagnetic ordering at 25 K. The possible spin arrangements in the system are also suggested.
    Inorganic Chemistry 03/2013; 52(5):2492-6. · 4.59 Impact Factor
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    ABSTRACT: 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 57Fe 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.
    Dalton Transactions 03/2013; · 3.81 Impact Factor
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    ABSTRACT: A new NiO-based material Pb(2)Ni(PO(4))(2) was obtained by a conventional solid-state reaction in air. The crystal structure exhibits both corner- and edge-sharing {Ni-O-P} bonds in the system. Magnetic properties were investigated by means of magnetic susceptibility, magnetization, and heat capacity measurements. The results show a typical three-dimensional antiferromagnetic ordering below ∼4 K and a field-induced spin-flop transition below the Néel temperature.
    Dalton Transactions 02/2013; · 3.81 Impact Factor
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    ABSTRACT: A new small-pore compound K(4)Fe(4)P(5)O(20) was obtained by conventional solid-state reaction in a closed crucible. The crystal structure is constructed by Fe(4)P(5)O(20) units forming chains along the c axis and elliptical eight-ring channels on the a-b plane in which K cations locate inside. Such structural characteristics seem to be quite similar to those seen in the natrolite family. However, Fe ions in K(4)Fe(4)P(5)O(20) have trigonal-bipyramidal instead of common tetrahedral coordination. Furthermore, our experimental results combined from magnetic susceptibility and (57)Fe Mössbauer spectrum measurements show mixed valence Fe(3+)/Fe(2+) in the titled material. To the best of our knowledge, this is the first example that contains mixed valence iron ions in a so-called natrolite framework.
    Inorganic Chemistry 06/2012; 51(14):7469-71. · 4.59 Impact Factor
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    ABSTRACT: Incorporating silver in ZnO has attracted a lot of interest in recent years to fabricate p-type ZnO, as the naturally occurring ZnO is n-type material due to its native defects such as zinc interstitials and oxygen vacancies. In this work, the structural, electronic, and optical properties of pure and Ag-doped (8, 0) ZnO SWNTs were investigated by using density functional theory (DFT). The optimized structures present buckling side wall surfaces. The configurations with Ag atoms replacing Zn atoms are p-type semiconduction materials while the configuration with Ag atom added out of the surface of ZnO SWNTs is n-type semiconduction material. The optical properties based on dielectric function and absorption coefficient were discussed. It was found that the Ag-doped (8, 0) ZnO SWNTs have absorption in the visible-light region, and the absorption intensity is enhanced with the increase of Ag concentration. Our results indicate that the Ag-doped ZnO nanotubes could have a better performance as a photocatalyst. The calculations of Ag-doped ZnO slabs terminated with (10−10) surfaces are also presented to simulate the crystalline nanotubes synthesized in experiments, and the results are compared with that of ZnO SWNTs.
    The Journal of Physical Chemistry C. 02/2011; 115(7).
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    ABSTRACT: A CuO-based material Cu(5)V(2)O(10) was successfully grown in a closed crucible using Sr(OH)(2)·8H(2)O as flux. The structure of Cu(5)V(2)O(10) can be viewed as being composed of two types of zigzag Cu-O chains running along the b- and c-axes, which shows a two-dimensional crosslike framework with 12-column square tunnels along the a-axis. Magnetic measurements show that Cu(5)V(2)O(10) exhibits unexpected large magnetic anisotropy, which is the first time magnetic anisotropy energy of ∼10(7) erg/cm(3) in the CuO-based materials has been observed. The origins of large anisotropy are suggested to arise from strong anisotropic exchanges due to the particular bonding geometry and the Jahn-Teller distortion of Cu(2+) ions. Further, the band structure investigated by the GGA+U method suggests that Cu(5)V(2)O(10) is a semiconductor.
    Journal of the American Chemical Society 02/2011; 133(5):1298-300. · 10.68 Impact Factor
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    ABSTRACT: We report the frequency-dependent third-order polarizabilities (γ) of a series of hydrogen-capped silicon clusters obtained using time-dependent density functional theory. We find that the magnitude of γ increases with a decrease in silicon cluster size, while the sign of γ at low input photon energy changes from positive to negative when the ratio of hydrogen saturation increases. At higher input photon energy, the sign of γ is determined mainly by cluster size. Our results rationalize several recent experiments on the optical properties of silicon nanostructures and are helpful for designing opto-electronic devices based on them.
    Chemical Physics Letters 01/2011; 509(4):124-128. · 2.15 Impact Factor
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    ABSTRACT: The structural, electronic and optical properties of carbon nitride (CN) nanotubes (CNNTs) built from triazine units were investigated by using density-functional theory (DFT) within the generalized gradient approximation. The total energies per CN unit (relative values) of armchair CNNTs are smaller than those of zigzag CNNTs for the same tube index. This leads to unsmooth tubular surfaces for nitrogen-nitrogen lone pair repulsions and porous structures. The armchair CNNTs appear as polygons while zigzag CNNTs are circles. Both the armchair and zigzag CNNTs are direct band gap semiconductors and their band gaps are dependent on tube size and chirality. The calculated dielectric functions of CNNTs are dependent on tube size and the directions of polarization. Moreover, they may be used as photocatalysts to split water to produce hydrogen.
    Nanotechnology 05/2010; 21(19):195702. · 3.84 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: 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).
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    Dan Zhao, Feifei Li, Wendan Cheng, Hao Zhang
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    ABSTRACT: Explorations of the A(1+)-RE(3+)-Mo(6+)-O(2-) (A(1+) is an alkali metal cation, RE(3+) is a rare-earth metal cation) quaternary systems prepared by the high-temperature solution growth method led to the title structure, sodium erbium bis-(molyb-date), NaEr(MoO(4))(2). It is isostructural to the scheelite structure (CaWO(4)) and is composed of [MoO(4)](2-) tetra-hedra with symmetry and [(Na/Er)O(8)](14-) polyhedra. The [(Na/Er)O(8)](14-) polyhedron is a distorted tetra-gonal anti-prism, also with symmetry, with statistically mixed Na/Er atoms at its centre. There are two sets of Na/Er-O bond lengths [2.420 (4) and 2.435 (3) Å], but just one set of Mo-O bond lengths [1.774 (4) Å].
    Acta Crystallographica Section E Structure Reports Online 01/2010; 66(Pt 5):i36. · 0.35 Impact Factor
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    Dan Zhao, Feifei Li, Wendan Cheng, Hao Zhang
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    ABSTRACT: The mixed-metal rare-earth polyphosphate LiSm(PO(3))(4) consists of a three-dimensional framework in which zigzag [(PO(3))(n)](n-) chains with a periodicity of four PO(4) tetrahedra are connected through Li(+) and Sm(3+) ions (both with 2. symmetry).
    Acta Crystallographica Section E Structure Reports Online 01/2010; 66(Pt 2):i3. · 0.35 Impact Factor
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    ABSTRACT: no abstract.
    Chemistry - An Asian Journal 08/2009; 4(10):1530-5. · 4.57 Impact Factor
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    ABSTRACT: Single crystals of CoV(2)O(6) were obtained in a closed crucible using a flux method. Magnetic measurements showed that this material displays a large magnetic anisotropy and a 1/3 magnetization plateau under a magnetic field applied along the c axis.
    Journal of the American Chemical Society 07/2009; 131(22):7554-5. · 10.68 Impact Factor