Structural,Electronic and Optical Properties of the Monoclinic α-CoV_2O_6

First-principles calculations based on density functional theory are performed to investigate the structural,electronic and optical properties of monoclinic α-Co V2O6.Firstly,the geometry structures obtained by geometry optimization are consistent with the experimental values.Then,the energy band structure is studied using both GGA and GGA+U methods.It is found that the on-site Coulomb repulsion of the Co 3d orbital plays a key role in describing the electronic properties of α-Co V2O6,and is necessary to open the energy band gap.According to the partial density of states(PDOS),significant Co–O and V–O hybridizations are observed in the valence and conduction bands,respectively.Furthermore,the Co–O and V–O bonds are found to have significant covalent characters.Below the absorption threshold ~1.9 e V,no absorption can be detected.However,there exists a strong and wide absorption band in the energy range from 1.9 to 11 e V.Such novel optical properties imply that the α-Co V2O6 may have some potential optical applications.     

Electronic Structures and Optical Properties of HgGa_2X_4 （X=S,Se,Te）Semiconductors

The first-principles density functional calculations are performed to study the geometries and electronic structures of HgGa2X4（X = S,Se,Te） semiconductors with defect chalcopyrite structures,and the optical properties of all crystals are investigated systematically.The results indicate that these compounds have similar band structures and the band gap decreases from S to Se to Te.For the linear optical properties,three crystals show good light transmission in the IR and part visible regions,and in particular,HgGa2S4 and HgGa2Se4 crystals possess moderate birefringence.For the nonlinear optical properties,these crystals have stronger second harmonic generation（SHG）,and are theoretically predicted to have larger second-order static SHG coefficients（ 30 pm/V）.The SHG of HgGa2X4（X = S,Se,Te） semiconductors can be attributed to the transitions from the bands near the top of valence band derived from X（X = S,Se,Te） p states to the unoccupied bands contributed by the p states of Ga atoms.Our results indicate that the HgGa2S4 and HgGa2Se4 compounds are good candidates for nonlinear optical crystals in the IR region.     

Effect of Zr and C Co-doping on the Optical Properties and Electronic Structure of TiO_2

The systematic trends and effect introduced by Zr and C co-doping to TiO2 of electronic structure and optical properties of anatase TiO2 have been calculated by the plane-wave ultra-soft pseudopotential density functional theory (DFT) method within the generalized gradient approximation (GGA) for the exchange-correlation potential. Through the current calculations, the density of states (DOS), energy band structure and optical absorption coefficients have been obtained for TiO2 and compared with the doped TiO2, and the influence of electronic structure and optical properties caused by Zr and C co-doping has been presented qualitatively together. The results revealed that the energy band gap has been decreased owing to the doped Zr and C, whereas the optical absorption coefficients have been increased in the region of 400～800 nm and a red shift of absorption band can be found. Accordingly, photo catalytic activity of TiO2 has been enhanced. The current calculations are in good agreement with the experimental data.     

Li3AlB2O6： Synthesis, Crystal Structure, and Its Luminescence Property Compared with LiSrBO3

The synthesis and crystal structure of Li3AlB2O6 with different cell parameters are reported and these cells are transformed each other from the confirmation of crystallographic structural analyses. The absorption spectrum, luminescence and lifetimes of the Li3AlB2O6 and LiSrBO3 solid compounds are measured and the comparisons are made between them. It is shown that the absorption edges are at about 400 nm (or band gap 3.1 eV) and there is one of absorption peaks at about 350 nm for the Li3AlB2O6 and LiSrBO3. The emission band (530 nm) makes a red shift and fluorescence decay time (24.39 ns) of the Li3AlB2O6 becomes smaller compared with the emission band (480 nm) and lifetime (93.16 ns) of the LiSrBO3 at the visible region. The transition energies and oscillator strengths of the clusters (Li3AlB2O6)2 and (LiSrBO3)2 lying at low excited states are calculated by the time-dependent Hartree-Fock method. The obtained results are used to model the photophysical properties and discuss the origin of spectral bands of the Li3AlB2O6 and LiSrBO3.     

The First-principlies Calculations of the Electronic Structures and Optical properties of Ⅱ-Ⅲ2-Ⅵ4 （Ⅱ=Zn,Cd; Ⅲ= In; Ⅵ=Se,Te）

The electronic structures and optical properties of II-III2-VI4 （II = Zn, Cd; III = In; VI = Se, Te） compounds are studied by the density functional theory （DFT） using the Vienna ab initio simulation package （VASP）. Geometrical optimization of the unit cell is in good agreement with the experimental data. Our calculations show that the valence band maximum （VBM） and conduction band minimum （CBM） are located at G resulting in a direct energy gap. The optical properties are analyzed, and the independent second harmonic generation （SHG） coefficients are determined. By an analysis of the band structure, we can get that SHG response of the system can be attributed to the transitions from the bands near the top of valence band that are derived from the Se/Te p states to the unoccupied bands contributed by the p states of In atoms.     

Electronic and Optical Properties of KNbO3,NaNbO3 and K0.5 Na0.5 NbO3 in Paraelectric Cubic Phase：a Comparative First-principles Study

The structural,electronic and optical properties of KNbO 3 (KN),NaNbO3(NN)and K05 Na0.5NbO3(KNN) in paraelectric cubic phase were calculated employing the plane-wave pseudopotential method based on density functional theory (DFT).The calculated electronic structures of the three crystals show similar features in the valence bands and the lower conduction bands.However,the structures in higher conduction bands differ markedly due to the effect of Na and K atoms.The calculated optical properties reveal that the features of optical spectrum at low energy are dominated by the transitions from O2p valence bands to Nb 4d conduction bands and those at high energy are related to the transitions to K 4s4p and/or Na 3s3p states.Moreover,the optical constants of KNN are approximately the average of KN and NN at high energy.Therefore,the optical properties of KNN in high energy region can probably be altered by changing the ratio of Na/K.     

Thienopyrazine or dithiadiazatrindene containing low band gap conjugated polymers for polymer solar cells

Four new low-band-gap alternating copolymers （P-1, P-2, P-3 and P-4） based on electron-rich benzodithiophene and newly developed electron-deficient units, thienopyrazine or dithiadiazatrindene derivatives, were synthesized by Stille polycondensation. All polymers exhibit good solubility in common organic solvents and a broad absorption band in the visible to near-infrared regions. The film optical band gaps of the polymers are in the range of 1.28-2.07 eV and the highest occupied molecular orbital （HOMO） energy levels are in the range of-4.99 eV to -5.28 eV. Bulk heterojunction polymer solar cells （PSCs） of the polymers were fabricated with phenyl-C61-butyric acid methyl ester （PC61BM） as acceptor material, and a power conversion efficiency of 0.80% was realized with P-1 as donor material.     

Evolution of Structural, Electronic and Optical Properties of Monoclinic ZrO2 under High Pressure： A First Principles Study

The structural, electronic and optical properties of the monoclinic ZrO2 were studied by ab initio calculations based on the density functional theory and pseudopotential method. The calculated lattice parameters and band gap are in agreement with the experimental and other theoretical values. The evolution of lattice parameters and electronic properties were illustrated under high pressure. Meanwhile, the optical properties, such as adsorption coefficients, imaginary part of dielectric function, and energy loss function, were investigated under both ambient and high pressures.     

Interaction of Photoactive[Fe（CN）6]4^- with TiO2 Anatase（101） Surface： A Periodic Density Functional Theory Study

The plane-wave pseudopotential function method,based on density-functional theory,has been used to calculate the adsorption,electronic band structures,orbitals and optical absorption spectrum of [Fe(CN)6]4-on TiO2 anatase(101) surface. Our calculations reveal that the surface-modified anatase system has large adsorption energy and a much narrower band gap. [Fe(CN)6]4-adsorption on the (101) surface could lead to a large red shift of the anatase optical absorption threshold,which extends into a visible region significantly. The calculated results are in agreement with the experiment and other theoretical studies reasonably. It is very important for the understanding and further development of photovoltaic materials that are active under visible light.     

Two-dimensional blue-phase CX(X=S,Se) monolayers with high carrier mobility and tunable photocatalytic water splitting capability

Photocatalytic water splitting utilizing solar energy is considered as one of the most ideal strategies for solving the ene rgy and environmental issues.Recently,two-dimensional(2 D) materials with an intrinsic dipole show great chance to achieve excellent photocatalytic performance.In this work,blue-phase monolayer carbon monochalcogenides(CX,X=S,Se) are constructed and systematically studied as photocatalysts for water splitting by performing first-principles calculations based on density functional theory.After confirming the great dynamical,thermal,and mechanical stability of CX monolayers,we observe that they possess moderate band gaps(2.41 eV for CS and 2.46 eV for CSe) and high carrier mobility(3.23 × 10~4 cm~2 V~(-1) s~(-1) for CS and 4.27 × 10~3 cm~2 V~(-1) s~(-1) for CSe),comparable to those of many recently reported 2 D photocatalysts.Moreover,these two monolayer materials are found to have large intrinsic dipole(0.43 D for CS and 0.51 D for CSe),thus the build-in internal electric field can be selfintroduced,which can effectively drive the separation of photongenerated carriers.More importantly,the well-aligned band edge as well as rather pronounced optical absorption in the visible-light and ultraviolet regions further ensure that our proposed CX monolayers can be used as high efficient photocatalysts for water splitting.Additionally,the effects of external strain on the electronic,optical and photocatalytic properties of CX monolayers are also evaluated.These theoretical predictions will stimulate further work to open up the energy-related applications of CX monolayers.     

Double NASICON-type cell: ordered Nd3+ distribution in Li0.2Nd0.8/3Zr2(PO4)3

The NASICON compound Li(0.2)Nd(0.8/3)Zr(2)(PO(4))(3), synthesized by a sol-gel process, has been structurally characterized by TEM and powder diffraction (neutron and X-ray). It crystallizes in the space group R3[combining macron] (No. 148): at room temperature, the Nd(3+) ions present an ordered distribution in the [Zr(2)(PO(4))(3)](-) network which leads to a doubling of the classical c parameter (a = 8.7160(3) A, c = 46.105(1) A). Above 600 degrees C, Nd(3+) diffusion occurs leading at 1000 degrees C to the loss of the supercell. This reversible cationic diffusion in a preserved 3D [Zr(2)(PO(4))(3)](-) network is followed through thermal X-ray diffraction. Ionic conductivity measurements have been undertaken by impedance spectroscopy, while some results concerning the sintering of the NASICON compound are given.     

Hydrothermal synthesis, crystal structure, and magnetic properties of a new inorganic vanadium(III) phosphate with a chain structure

A new vanadium(III) phosphate, Na3V(OH)(HPO4)(PO4), has been synthesized by using mild hydrothermal conditions under autogeneous pressure. This material represents a very rare example of sodium vanadium(III) phosphate with a chain structure. The crystal structure has been determined by refinement of powder X-ray diffraction data, starting from the atomic coordinates of an isotypic compound, Na3Al(OH)(HPO4)(PO4), which was obtained under high temperature and high pressure. The phase crystallizes in monoclinic space group C2/m (No. 12) with lattice parameters a = 15.423(9) A, b = 7.280(0) A, c = 7.070(9) A, beta = 96.79(7) degrees, V = 788.3(9) A(3), and Z = 4. The structure consists of one-dimensional chains composed of corner-sharing VO5(OH) octahedra running along the b direction. They are decorated by isolated PO4 and HPO4 tetrahedra sharing two of their corners with the ones of the vanadium octahedra. The interconnection between the chains is assured by three crystallographically distinct Na(+) cations. Magnetic investigation confirms the 3+ oxidation state of the vanadium ions and reveals an antiferromagnetic arrangement between those ions through the chain.     

夹心型钼磷酸盐的水热合成与晶体结构

采用水热法合成了首例含过渡金属铬的夹心型钼磷酸盐〔Ｈ３Ｎ（ＣＨ２）６ＮＨ３〕２Ｈ３｛Ｃｒ〔Ｍｏ６Ｏ１５（ＨＰＯ４）（Ｈ２ＰＯ４）３〕２｝·４Ｈ２Ｏ超分子化合物,用单晶Ｘ－射线测定其晶体结构,该晶体属三斜晶系,空间群Ｐ１。晶胞参数ａ＝１２．１５６（２）,ｂ＝１２．８０９（３）,ｃ＝１３．５３０（３）,α＝１０２．４６（３）°,β＝９３．６７（３）°,γ＝９３．４６（３）°．Ｖ＝２０４６．９（７）３,Ｚ＝１,Ｍｒ＝２７６８．６９,Ｄｃ＝２．２４６ｇ／ｃｍ３,Ｆ（０００）＝１３３７,μ＝２．１６２ｍｍ－１,全矩阵最小二乘法修正至Ｒ＝０．０６６６,ｗＲ＝０．１７４５,独立可观测点数为７１４２。化合物是分别由质子化的１,６－己二胺、水和｛Ｃｒ〔Ｍｏ６Ｏ１５（ＨＰＯ４）（Ｈ２ＰＯ４）３〕２｝７－阴离子构成,而｛Ｃｒ〔Ｍｏ６Ｏ１５（ＨＰＯ４）（Ｈ２ＰＯ４）３〕２｝７－是由２个〔Ｍｏ６Ｐ４〕与Ｃｒ３＋形成了６配位的夹心型阴离子     

Syntheses and Properties of New Layered Alkali-Metal/Ammonium Vanadium(V) Methylphosphonates: M(VO(2))(3)(PO(3)CH(3))(2) (M = NH(4), K, Rb, Tl). Single-Crystal Structures of K(VO(2))(3)(PO(3)CH(3))(2) and NH(4)(VO(2))(3)(PO(3)CH(3))(2)

The hydrothermal syntheses of a family of new alkali-metal/ammonium vanadium(V) methylphosphonates, M(VO(2))(3)(PO(3)CH(3))(2) (M = K, NH(4), Rb, Tl), are described. The crystal structures of K(VO(2))(3)(PO(3)CH(3))(2) and NH(4)(VO(2))(3)(PO(3)CH(3))(2) have been determined from single-crystal X-ray data. Crystal data: K(VO(2))(3)(PO(3)CH(3))(2), M(r) = 475.93, trigonal, R32 (No. 155), a = 7.139(3) ?, c = 19.109(5) ?, Z = 3; NH(4)(VO(2))(3)(PO(3)CH(3))(2), M(r) = 454.87, trigonal, R32 (No. 155), a = 7.150(3) ?, c = 19.459(5) ?, Z = 3. These isostructural, noncentrosymmetric phases are built up from hexagonal tungsten oxide (HTO) like sheets of vertex-sharing VO(6) octahedra, capped on both sides of the V/O sheets by PCH(3) entities (as [PO(3)CH(3)](2-) methylphosphonate groups). In both phases, the vanadium octahedra display a distinctive two short + two intermediate + two long V-O bond distance distribution within the VO(6) unit. Interlayer potassium or ammonium cations provide charge balance for the anionic (VO(2))(3)(PO(3)CH(3))(2) sheets. Powder X-ray, TGA, IR, and Raman data for these phases are reported and discussed. The structures of K(VO(2))(3)(PO(3)CH(3))(2) and NH(4)(VO(2))(3)(PO(3)CH(3))(2) are compared and contrasted with related layered phases based on the HTO motif.     

Synthesis and Crystal Structure of {4-[2-（9- Hexyl-9H-carbazol-3-yl）vinyl]phenyl} Dimethylamine

The title compound {4-[2-(9-hexyl-9H-carbazol-3-yl)vinyl]phenyl} dimethylamine has been synthesized by the well known Wittig reaction, and its crystal structure was determined by single-crystal X-ray diffraction analysis. It crystallizes in monoclinic, space group P21/c with a = 47.87(2), b = 10.222(4), c = 9.612(4) , β = 92.401(9)o, V = 4699(3) 3, Z = 8, C28H32N2, Mr = 396.56, Dc = 1.121 g/cm3, F(000) = 1712 and μ(MoKa) = 0.065 mm-1. The final R and wR are 0.0793 and 0.1983, respectively for 3524 observed reflections with I > 2σ(I). In the title compound, the bond lengths are normal, and the crystal is stabilized by Van der Waals’ forces.     

Synthesis and characterization of a new bisphosphonic acid and several metal hybrids derivatives

Commercial bis-(4-bromophenyl)-ether, [BrC(6)H(4)](2)-O, has been used to prepare 4-[4'-(diethoxyphosphoryl)phenoxy]phenyl-phosphonic acid diethyl ester, [(CH(3)CH(2))(2)O(3)P-C(6)H(4)](2)-O, (I) following a slight modification of the Michaelis-Arbuzov reaction. The acid hydrolysis of I gave 4-(4'-phosphonophenoxy)phenyl phosphonic acid, [H(2)O(3)P-C(6)H(4)](2)-O (II), and both compounds have been characterized by (1)H NMR and (13)C NMR. The crystal structure of II has been determined by single-crystal X-ray diffraction. II crystallizes in an orthorhombic unit cell, space group Pbcn, with a = 7.822(3) A, b = 5.821(2) A, c = 28.982(9) A, and V = 1319.7(7) A(3). The final R factor was R1 = 0.0614. The structure is layered, being held together through a hydrogen bonding network. II has been used as precursor in the syntheses of new metal (Mn, Fe, Co, Ni, Cu, and Zn) bisphosphonates. The syntheses were carried out using a fixed metal/bisphosphonic acid molar ratio of 2.1:1 and the influence of the pH in the reactions has been studied. Nine new compounds have been isolated: Mn(2)(O(3)PC(6)H(4)OC(6)H(4)PO(3)).1.5H(2)O (III), Mn(5)(OH)(2)(O(3)PC(6)H(4)OC(6)H(4)PO(3))(2).2H(2)O (IV), Fe(HO(3)PC(6)H(4)OC(6)H(4)PO(3)).0.5H(2)O (V), Co(2)(O(3)PC(6)H(4)OC(6)H(4)PO(3)).2H(2)O (VI), Ni(2)(O(3)PC(6)H(4)OC(6)H(4)PO(3)).3H(2)O (VII), Ni(2)(O(3)PC(6)H(4)OC(6)H(4)PO(3)).2H(2)O (VIII), Cu(2)(O(3)PC(6)H(4)OC(6)H(4)PO(3)) (IX), Zn(2)(O(3)PC(6)H(4)OC(6)H(4)PO(3)) (X), and Zn(HO(3)PC(6)H(4)OC(6)H(4)PO(3)H) (XI). Compound IX crystallizes in an orthorhombic unit cell, space group Pbcn, and unit cell parameters a = 8.1012(5) A, b = 5.3109(3) A, c = 29.2595(5) A, and V = 1258.8(1) A(3). Its structure has been solved by ab initio powder diffraction and refined by the Rietveld method to R(F) = 0.042. IX has a pillared layer framework with highly distorted CuO(5) groups sharing edges to give isolated dimers. XI was indexed in a monoclinic unit cell, space group P112(1), with parameters a = 9.4991(9) A, b = 5.0445(5) A, c = 29.131(2) A, gamma = 91.945(7) degrees, and V = 1395.1(3) A(3). Its structure has been refined by the Rietveld method, R(F) = 0.054, since it is isostructural with the known compound, Zn[HO(3)P(C(6)H(4))(2)PO(3)H]. All solids were also characterized by thermal analysis and IR and UV-Vis spectroscopies.     

A novel organic-inorganic hybrid based on an 8-electron-reduced Keggin polymolybdate capped by tetrahedral, trigonal bipyramidal, and octahedral zinc: synthesis and crystal structure of (CH3NH3)(H2bipy)[Zn4(bipy)3(H2O)2MoV8MoVI4O36)(PO4)].4H2O

Hydrothermal reaction of H(3)PO(3), CH(3)NH(2), zinc(II) acetate, 4,4'-bipyridine (bipy), and (NH(4))(6)Mo(7)O(24).4H(2)O at 180 degrees C led to a novel organic-inorganic layered hybrid, [CH(3)NH(3)][H(2)bipy][Zn(4)(bipy)(3)(H(2)O)(2)Mo(V)(8)Mo(VI)O(36)(PO(4))].4H(2)O (1). Its structure was established by single-crystal X-ray diffraction. It crystallizes in the monoclinic space group P2(1)/c with cell parameters of a = 17.3032(2), b = 17.8113(3), and c = 23.4597 (4) A, beta = 106.410(1) degrees, V = 6935.6(2) A(3), and Z = 4. The structure of compound 1 features a novel 2D layer built from the 8e-reduced tetracapped Keggin [Zn(4)Mo(12)O(36)(PO(4))](3)(-) anions, which are further interconnected by bridging bipy ligands. The four zinc(II) ions are in tetrahedral, trigonal bipyramidal, and octahedral coordination geometries, respectively.     

新型磷酸钒孔道结构化合物(H3NCH2CH2NH3)3- [ (VO)4(PO4)2 (HPO4)4]的水热 合成及结构表征

以有机分子乙二胺作为模板剂合成了新型磷酸钒孔道化合物(H3NCH2CH2NH3)3^-[(VO)4(PO4)2(HPO4)4,并通过X射线单晶衍射实验进行了结构表征,晶体学数据为：C2/c,a=1.8505(9)nm,b=0.7089(4)nm,c=2.3304(10)nm,β=96.43(3)°,V-3.038(3)nm^3,Z=8,R=0.067,Rw^b=0.1635,该化合物具有非常独特和规整的二维孔道骨架结构,进一步的晶体化学研究表明该化合物为一新的VPO物相。     

Synthesis and Crystal Structure of 2-Methoxy-benzoic Acid 2-Oxo-3-（2,4,6-trimethyl-phenyl）-1-oxa-spiro[4.4]non-3-en-4-yl Ester

The new title compound 2-methoxy-benzoic acid 2-oxo-3-(2,4,6-trimethyl-phenyl)-1-oxa-spiro[4.4]non-3-en-4-yl ester(3,C25H26O5) has been synthesized by the condensation reaction of 4-hydroxy-3-(2,4,6-trimethyl-phenyl)-1-oxa-spiro[4.4]non-3-en-2-one(2) with 2-methoxylben-zoyl chloride,and characterized by 1H NMR and MS spectra.Its crystal structure was determined by single-crystal X-ray diffraction.The crystal is of monoclinic,space group P21/c with a = 10.6945(7),b = 12.8176(7),c = 16.4223(10) ,β = 103.5665(17)o,V = 2188.3(2) 3,Z = 4,Dc = 1.234 g/cm3,F(000) = 864.000,μ = 0.085 mm-1,the final R = 0.0520 and wR = 0.1132 for 2732 observed reflections with I 2σ(I).In the crystal structure,the C(1)-C(2)(1.478 ) bond is significantly shorter than the normal single C-C bond(1.53 ),suggesting that the carbonyl group on C(1) has formed a conjugated system with a double bond on C(2) and C(12).     

A Pseudo-Keggin Compound:Hydrothermal Synthesis and Crystal Structure of (DETAH)(DETAH3)3[V18O42(PO4)]·(PO4)·2H2O

The novel vanadophosphate (DETAH)(DETAH3)3[V18O42(PO4)]·(PO4)·2H2O has been synthesized under hydrothermal conditions and its structure was determined by single-crystal X-ray diffraction. The compound crystallizes in monoclinic, space group C2/c with a=23.857(3), b=12.9619(18), c=20.204(3) (A), β=105.692(2)°, V=6015.0(14) (A)3, Z=4, Dc=2.473 g/cm3, Mr=2239.68, F(000)=4432, R=0.0725, wR=0.1524 and GOOF=1.095. The metaloxo cluster contains a novel six-capped pesudo-Keggin structure unit which encloses a disorder PO43- guest.