呋喃同系物C4H4X(X=O,S,Se,Te)非线性光学性质的TDDFT-SOS理论研究

用含时密度泛函理论(TD-DFT)组合态求和(SOS)方法计算了呋喃同系物[呋喃(C4H4O)、噻吩(C4H4S)、硒吩(C4H4Se)、碲吩(C4H4Te)]的非线性光学性质.计算结果表明,体系的三阶NLO系数(γ)随着杂原子被重原子的取代而逐步增大,B3LYP等4种势函数计算的NLO系数基本一致.计算的色散关系曲线表明,标题化合物在宽频区存在小的色散作用,是一类具有应用前景的NLO材料.     

Laser Desorption Ionization of As<Subscript>2</Subscript>Ch<Subscript>3</Subscript> (Ch = S,Se, and Te) Chalcogenides Using Quadrupole Ion Trap Time-of-Flight Mass Spectrometry: A Comparative Study

Laser desorption ionization using time-of-flight mass spectrometer afforded with quadrupole ion trap was used to study As₂Ch₃ (Ch = S, Se, and Te) bulk chalcogenide materials. The main goal of the study is the identification of species present in the plasma originating from the interaction of laser pulses with solid state material. The generated clusters in both positive and negative ion mode are identified as 10 unary (S _p ^+/– and As _m ^+/– ) and 34 binary (As _m S _p ^+/– ) species for As₂S₃ glass, 2 unary (Se _q ^+/– ) and 26 binary (As _m Se _q ^+/– ) species for As₂Se₃ glass, 7 unary (Te _r ^+/– ) and 23 binary (As _m Te _r ^+/– ) species for As₂Te₃ material. The fragmentation of chalcogenide materials was diminished using some polymers and in this way 45 new, higher mass clusters have been detected. This novel approach opens a new possibility for laser desorption ionization mass spectrometry analysis of chalcogenides as well as other materials.

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Structure and spectral-optical characteristics of Se,Se/CdS,and Se/Cd<Subscript>0.5</Subscript>Zn<Subscript>0.5</Subscript>S nanoparticles,stabilized in polymer-containing media

A method was proposed for the production of colloidal nanoparticles of selenium stabilized by polymers and surfactants, and their structural and optical characteristics were studied. It was shown that during the deposition of CdS and Cd_0.5Zn_0.5S on the surface of the Se nanoparticles followed by dissolution of the selenium with sodium sulfite it is possible to obtain network “nanoframeworks” with size 30–50 nm, formed by CdS or Cd_0.5Zn_0.5S particles measuring 3–5 nm. __________ Translated from Teoreticheskaya i éksperimental’naya Khimiya, Vol. 43, No. 1, pp. 24–29, January–February, 2007.     

黄铜矿型半导体材料CuAlX2 (X=S,Se, Te)的电子结构和光学性质

采用基于赝势平面波基组的密度泛函理论方法,研究具有黄铜矿结构的CuAlX2(X=S,Se,Te)晶体的电子结构,并预测了它们的线性和非线性光学性质.结果表明:这些化合物具有相似的能带结构,带隙随X原子从S→Se→Te依次减小.三种晶体的静态介电常数、静态折射率和静态倍频系数d36的变化情况与带隙的变化相反,随着X原子自S→Se→Te改变依次递增,但静态双折射率依次递减.该系列化合物的倍频效应主要来源于价带顶附近的占据能带向以Al和X原子的p电子态为主要成分的空带之间的跃迁.在三种晶体中,CuAlTe2除静态双折射率偏小外,其它光学性能要优于CuAlS2和CuAlSe2.     

Synthesis,structure, and properties of V<Subscript>2</Subscript>O<Subscript>3</Subscript>(XO<Subscript>4</Subscript>)<Subscript>2</Subscript> (X = S,Se)

Compounds described as V₂O₃(XO₄)₂, where X = S or Se, were prepared from vanadium(V) oxide mixtures with concentrated sulfuric and selenic acids. The physicochemical properties of the products were studied; for V₂O₃(SeO₄)₂, the crystal structure was determined by powder X-ray diffraction and neutron diffraction, and its key differences from the structure of V₂O₃(SO₄)₂ were identified. V₂O₃(SeO₄)₂ crystallizes in the monoclinic system with the unit cell parameters a = 15.3831(2)Å, b = 5.54096(5)Å, c = 9.71644(7)Å, β = 111.886(1)°, V = 768.51ų, space group C2/c (no. 15).     

Structures and electronic properties of C<Subscript>12</Subscript>Si<Subscript>8</Subscript>X<Subscript>8</Subscript> (X = H,F, and Cl)

The structural stabilities and electronic properties of C₁₂Si₈X₈ where X = H, F, and Cl are probed on the basis of density functional theory at the B3LYP/6-311++G**//B3LYP/6-31+G* level. Vibrational frequency calculations show that all the systems are true minima. The infrared spectra of the most stable C₁₂Si₈X₈ molecules are simulated to assist further experimental characterization. The functionalized structures and energy gaps between the highest occupied molecular orbital, HOMO, and the lowest unoccupied molecular orbital, LUMO, have been systematically investigated. It seems that C₁₂Si₈H₈ has more stability against electronic excitations via increasing the HOMO–LUMO gap comparing with C₁₂Si₈Cl₈ and C₁₂Si₈F₈. High charge transfer on the surfaces of our stable compounds, provokes further investigations on their possible application for hydrogen storage. The addition reaction energies of C₁₂Si₈X₈ are high exothermic, and C₁₂Si₈F₈ is more thermodynamically accessible.     

Crystal chemistry of AB2X4 (X = S,Se, Te) compounds

An attempt is made to correlate the crystal structures of ternary chalcogenides of composition AB₂X₄ with the cationic radius ratio and a pseudo force-constant involving their electronegativities. The resultant diagram adequately resolves structures based on the types K₂SO₄, monoclinic, olivine, MnY₂S₄, Th₃P₄, and CaFe₂O₄ but structure types based on spinel, Cr₃Se₄, and Ag₂HgI₄ are not resolved. Crystal chemical arguments are used to explain these observations and to advance reasons for the successes and failures of this method for predicting structure types.     

Ionic conduction and chemical diffusion in solid solutions of superionic conductors Cu<Subscript>2</Subscript>X-Me<Subscript>2</Subscript>X (Me = Ag,Li; X = S,Se)

Ionic conduction and chemical diffusion in silver-and lithium-substituted superionic copper selenides and sulfides are studied. Upon substitution of lithium for copper, a strong increase in the activation energy of ionic conduction in copper sulfide and selenide and the concomitant several-fold decrease in the ionic conductivity are observed. The reasons for the deterioration of ionic transport conditions are elucidated. In contrast to the substitution of lithium for copper, the substitution of silver leads to higher ionic conductivity and the appearance of superionic conduction by two types of cations. Structural aspects of diffusion are considered. Different consequences of substitution of atoms into the cationic sublattice are associated with different electronic sheaths of lithium (alkali metal), silver, and copper (noble metals), which give rise to different types and degrees of hybridization of valence electrons of atoms in the disordered sublattice and the anionic frame.     

Bifunctional decamethylcyclohexasilanes X<Subscript>2</Subscript>Si<Subscript>6</Subscript>Me<Subscript>10</Subscript> (X = Cl,H, or OH): molecular and crystal structures and mesomorphic properties

Isomer separation of mixtures, which were prepared by chlorination followed by transformations of dodecamethylcyclohexasilane (Me₂Si)₆ into bifunctional decamethylcyclohexasilanes X₂Si₆Me₁₀ (X = Cl, H, or OH), was carried out. As a result, mixtures of the corresponding 1,3- and 1,4-derivatives were separated to obtain structural isomers, and stereoisomers, viz., cis- and trans-1,4-dihydrocyclohexasilanes, were isolated in individual form. The molecular and crystal structures of the resulting bifunctional decamethylcyclohexanes X₂Si₆Me₁₀ (X = H or OH) and decamethyl-7-oxahexasilanorbornane were established by X-ray diffraction analysis. Bifunctional cyclohexasilanes form a mesophase as a plastic crystal. The temperature range of its existence was determined. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 7, pp. 1566–1575, July, 2005.     

Thermal Decomposition of Ti<Subscript>5</Subscript>(Se,Te)<Subscript>8</Subscript> in Argon and Nitrogen Atmospheres

Chalcogenides TiSe_1.60−x Te_x (0 ≤ x ≤ 1.60), forming a continuous series of hexagonal solid solutions, were prepared by the direct ampule procedure. The thermal decomposition of TiSe_1.60−x Te_x was studied for the samples with x = 0, 0.16, 0.80, 1.44, and 1.60 in Ar and N₂ atmospheres in the course of heating from 25 to 1000°C. The selenide undergoes no weight loss under Ar, in contrast to the telluride which disproportionates and loses weight owing to the formation of volatile TiTe₂. At high temperatures, tellurides are more sensitive than selenides to the presence of nitrogen: The disproportionation is accompanied by the reaction of TiTe₂ with N₂, yielding low-volatile titanium nitride and free tellurium. Titanium selenide and telluride as components of the solid solutions behave similarly to the corresponding individual chalcogenides.__________Translated from Zhurnal Obshchei Khimii, Vol. 75, No. 7, 2005, pp. 1063–1067.Original Russian Text Copyright © 2005 by Pankratova, Zvinchuk, Suvorov, Hatanpaa, Kozlov, Leskela.     

Synthesis,Structure and Isomerism of the [Fe<Subscript>3</Subscript>Pt(μ<Subscript>4</Subscript>-Q)(CO)<Subscript>9</Subscript>(dppm)] Clusters (Q = Se,Te; dppm = Ph<Subscript>2</Subscript>PCH<Subscript>2</Subscript>PPh<Subscript>2</Subscript>)

The reaction of K₂[Fe₃(μ₃-Q)(CO)₉] (Q = Se (K₂[1a]), Te (K₂[1b])) with [(dppm)PtCl₂] leads to the addition of a [(dppm)Pt]²⁺ unit to a Fe₂Q face of the initial cluster. By this way new heteronuclear clusters [Fe₃Pt(μ₃-Q)(CO)₉(dppm)] were obtained possessing a butterfly-shaped cluster core bridged by a μ₄-Q unit. It has been found that the resulting Fe-Pt clusters exist as equilibrium mixtures of two isomeric forms in solution differing by the dppm coordination mode: as a chelate ligand coordinated to Pt or as a bridging ligand coordinated to Pt and Fe atoms. The mixtures of isomers can be separated by chromatography and the pure isomers can be isolated as stable crystalline phases. Solutions of both isomers attain equilibrium at normal conditions in about 1 month as found by NMR. Dedicated to Professor Dieter Fenske in the occasion of his 65th birthday.     

硫族桥原子对类立方烷簇[Fe_4X_4](X=S、Se、Te)成键特征的影响

本文用EHMO法对[Fe_4X_4(SPh)_4]~(3-)和(Fe_4X_4(NO)_4](X=S、Se、Te)等六个类立方烷型簇合物的电子结构进行了计算,并分析讨论了桥基改变对这些类立方烷电子结构和成键特征的影响。结果表明,桥基S被Se、Te取代后前线区域分子轨道中桥基成份明显增大,能级普遍升高;Fe—X键强度减弱,Fe—Fe间作用稍有增强;能级间隔△E(LUMO—HOMO)则随端基配体类型的不同而增大或减少。     

氧族桥原子对类立方烷簇[Mo_4X_4Cp_4′]成键特征的影响(X=O,S,Se,Te;Cp′=Cp or Pr~iCp)

本文用EHMO法对(Mo_4X_4Cp′4](X=0,S,Se,Tc)四个类立方烷型簇合物的电子结构进行了计算,结果表明,桥基X从O到Te,前线区域分子轨道中桥基成分明显增加,能级普遍升高;Mo-Mo间作用有所增强;能隙ΔE(LUMO-HOMO)增大;Mulliken键级P的次序为P_(Mo-Se)>P_(Mo-S)>P_(Mo-Tc)>P_(Mo-o)>P_(Mo-Mo),说明第二过渡系元素Mo更倾向于与较重的se桥结合形成类立方烷型簇合物。     

Thermal decomposition studies of [Ni(NH<Subscript>3</Subscript>)<Subscript>6</Subscript>]X<Subscript>2</Subscript> (X = Cl,Br) in the solid state using TG-MS and TR-XRD

Detailed investigation on the thermal behaviour of hexaamminenickel(II) chloride and hexaamminenickel(II) bromide has been carried out by means of simultaneous TG/DTA coupled online with mass spectroscopy (TG-MS) and temperature-resolved X-ray diffraction (TR-XRD). Evolved gas analyses by TG-MS revealed the presence of NH₂, NH, N₂ and H₂ fragments in addition to ammonia during the deamination process. These transient species resulted due to the fragmentation of the evolved ammonia during pyrolysis. The intermediates formed during the thermal deamination stages were monitored by in situ TR-XRD. The final product of the decomposition was found to be nano size metallic nickel in both cases. Morphology of the complexes, intermediates and the residue formed at various decomposition stages was analysed by scanning electron microscope (SEM). Kinetic analyses using isoconversional method for deamination and dehalogenation reaction show that the activation energies vary with the extent of conversion, indicating the multi-step nature of these solid state decomposition reactions.     

Coordination Polyhedra RuXn (X = O,S, Se,Te) in Crystal Structures

Crystal-chemical analysis of 312 compounds containing complexes [Ru _a X _b ] ^z– (X = O, S, Se, Te) is performed using Voronoi–Dirichlet polyhedra (VDP) and the method of intersecting spheres. In most of these complexes, Ru atoms have coordination number (CN) 6 and form RuX₆ octahedra. However, only with respect to oxygen do the Ru(V)–Ru(VII) atoms exhibit CN 5 or 4 with trigonal-bipyramidal and tetrahedral coordination, respectively.The effect of the valence state of the Ru atoms on their stereochemistry is considered. The important role of the Ru–Ru interactions in the structure of the Ru(II)–Ru(V) compounds is established. As a result of the Ru–Ru interactions, the RuX₆ octahedra are linked through a face or common edge or give O₅Ru–RuO_- dimers in which every metal atom occupies one of the vertices of an octahedron formed by the neighboring Ru atom.The dependence of the Ru–Ru and Ru–O bond orders on their lengths is established on the basis of a crystal-structure analysis and the 18-electron rule.     

Mechanisms of [1,3]-Sigmatropic Migrations of the Nitroso Group in the ON-X-CH=X Systems (X = O,S, Se,NH, CH<Subscript>2</Subscript>)

[1,3]-Sigmatropic migrations of the nitroso group in the systems ON-X-CH=X (X = O, S, Se, NH, CH₂) were studied by MP2(fc)/6-311+G** and B3LYP/6-311+G** quantum-chemical calculations. The energy barrier in the process was estimated at 2.4 (2.5), 20.0 (25.0), and 22.3 (23.4) kcal/mol for X = O, NH, and CH₂, respectively. The energy minima for X = S and X = Se correspond to cyclic structures with two-coordinate NO group, which are more stable than acyclic structures by 9.3 (4.3) (X = S) or 13.1 (5.7) kcal/mol (X = Se).     

The RhX n (X = S,Se, Te) Coordination Polyhedra in Crystal Structures

The Voronoi–Dirichlet polyhedra (VDP) and the method of intersecting spheres were applied to crystal-chemical analysis of all known compounds whose structures contain rhodium atoms surrounded by chalcogen atoms. The influence of the rhodium valence state and the nature of the chalcogen on the main features of Rh stereochemistry are discussed. Rhodium atoms exhibit coordination numbers of 6, 5, or 4 with respect to S, Se, or Te atoms; in addition to the bonds with chalcogens, rhodium can form 1 to 4 bonds with metal atoms. The VDP volume for Rh(III), Rh(2.67), and Rh(II) atoms in selenides and tellurides very weakly depends on the valence state, whereas in the case of sulfides, the volume increases rather regularly with a decrease in the metal oxidation number from Rh(III) to Rh(I).     

The PtX n Coordination Polyhedra (X = S,Se, Te) in Crystal Structures

Using the Voronoi–Dirichlet partition procedure and the method of intersecting spheres, it is demonstrated that in the crystal structures of chalcogen-containing compounds, Pt(IV) atoms form only PtX₆ octahedra (X = S, Se, Te), whereas in the case of Pt(III) and Pt(II), square coordination by X atoms is typical. The Pt(II) atoms can also form PtX₅ square pyramids (X = S, Se), PtS₆ octahedra, and PtTe₃Pt₃ quasi-octahedra in which a platinum atom is located in the trans-position to each coordinated tellurium atom. It was found that Pt(II) atoms in the PtX₄ squares (X = S, Se), unlike square-coordinated Pt(III) atoms, can form one or two Pt–M bonds (M is a d metal) and 1 to 4 secondary Pt–Q bonds, where Q is an s metal or hydrogen. The main features of platinum stereochemistry depending on the metal valence state and coordination number (CN) and on the nature of the chalcogen atom were quantitatively characterized in terms of the Voronoi–Dirichlet polyhedra.