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1.
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.  相似文献   

2.
2-(2,3-Dihydroxpropyliminomethyl)6-methoxyphenol(H_3L), trimethylacetic acid(Hpiv), Gd(NO_3)3·6 H_2O and Co(NO_3)2·6 H_2O were reacted in Me OH to obtain a heterometallic tetranuclear cluster [Gd_2Co_2(L)_2(μ_3-OH)_2(piv)_6]·2 Hpiv·2 CH_3OH(1). X-ray crystallographic analysis reveals that compound 1 was found to be a butterfly heterometallic tetranuclear cluster. The crystal(C_(64)H_(108)Co_2Gd_2N_2O_(28), Mr = 1785.88) belongs to the triclinic crystal system, space group P1 with a =11.9798(6), b = 12.0877(5), c = 15.0367(7) ?, α = 67.320(4)°, β = 81.583(4)°, γ = 75.201(4)°, V =1939.62(18) ?3, Z = 1, T = 293.15 K, R = 0.048 and w R = 0.144 for 16299 observed reflections with I 2σ(I). In magnetization study, heterometallic 1 exhibits magnetocaloric effect(MCE) of 14.75 J·kg~(-1)·K~(-1) at 2 K for ΔH = 5 T, while it does not show non-linear response of the ac-susceptibilities.  相似文献   

3.
陈冰昆  钟海政  邹炳锁 《化学进展》2011,23(11):2276-2286
半导体纳米晶是近年来发展起来的一类新型功能材料,因其独特的量子限域效应和光电性质,在太阳电池、发光二极管、光电探测器、生物标记、非线性光学等领域中具有潜在的应用。与目前研究比较多的Ⅱ-Ⅵ和Ⅳ-Ⅵ族纳米晶相比,Ⅰ-Ⅲ-Ⅵ族半导体纳米晶,不含镉和铅等重金属元素,具有毒性小、带隙窄、光吸收系数大、Stokes位移大、自吸收小以及发光波长在近红外区等特点,有望成为新一代低成本太阳电池和低毒荧光量子点生物标记材料, 还可用于发光二极管和光电探测等领域。因此,Ⅰ-Ⅲ-Ⅵ族半导体纳米晶的合成、性质及应用研究成为近期纳米晶研究领域的热点之一。本文将综述Ⅰ-Ⅲ-Ⅵ族半导体纳米晶的研究进展,着重介绍其制备方法、光学性质及其在生物标记、太阳电池等领域的应用。  相似文献   

4.
The intramolecular process of Mg ( Ⅱ ) - , Sc ( Ⅲ ) - , Y ( Ⅲ ) - , In(Ⅲ)-and Pb ( Ⅱ )-trans-1,2-cyclohexanediaminetetraacetic acid (CyDTA) complexes was studied by the method of proton dynamic NMR(DNMR). The top limit of. the experimental temperature range of deuterium oxide solutions was extended from 100℃ to 167 ℃ instead of the previous 100 ℃ by using sealed, thick-walled tubes to observe experimental phenomena further. It was found that another intramolecular process, i. e. B, R (Bonded State, Rotational State) conversion, exists in these complexes formed by polyaminepolycarboxylic ligands in addition to △,A conversion and nitrogen inversion. A quantitative treatment was proposed to estimate the relative populations of acetate groups in B and R states.  相似文献   

5.
6.
The structure and the stability of pentazolide compounds $\hbox{A}_{\it n}(\hbox{N}_5)_{\rm 6-{\it n}}^{\it q}$ (A = B, Al, Si, P, and S; n= 1–3; q = +1, 0, ?1, ?2, and ?3), as high energy-density materials (HEDMs), have been investigated at the B3LYP/6-311+G* level of theory. The natural bond orbital analysis shows that the charge transfer plays an important role when the $\hbox{A}_{\it n}(\hbox{N}_5)_{\rm 6-{\it n}}^{\it q}$ species are decomposed to $\hbox{A}_{\it n}(\hbox{N}_5)_{\rm 5-{\it n}}\hbox{N}_3^{\it q}$ and N2. The more negative charges are transferred from the N2 molecule after breaking the N5 ring, the more stable the systems are with respect to the decomposition. Moreover, the conclusion can be drawn that ${\hbox{Al}(\hbox{N}_5)_5^{2-}}$ and ${\hbox{Al}_2(\hbox{N}_5)_4^{2-}}$ are predicted to be suitable as potential HEDMs.  相似文献   

7.
Reactions of lanthanoid trichlorides with sodium cyclopentylcyclopentadienyl in THFafford bis(cyclopentylcyclopentadienyl) lanthanoid chloride complexes (C_5H_9C_5H_4)_2LnCl(THF)_n (Ln=Nd, Sm, n=1; Ln= Er, Yb, n= 0). The compound [CP'_2SmCl(THF)]_2 (2) (Cp' =cyclopentylcy-clopentadienyl) crystallizes from mixed solvent of hexane and THF in monoclinic space group P_2_1/cwith a = 11.583 (3), b = 23.019(6), c = 8.227 (2), β= 90.26 (2)°, V= 2194 (1)~3, D_c= 1.59 g/cm~3.μ= 28.6 cm~(-1), F(000) = 1060, Z= 2 (dimers). Its crystal molecule is a dimer with a crystallographicsymmetry center. The central metal atom Sm is coordinated to two Cp' rings, two bridging chlorineatoms and one THF forming a distorted trigonal bipyramid. The crystal of [Cp'_2ErCl]_2 (3) belongs tothe triclinic space group P with a = 11.264 (2), b= 13.296(5), c = 14.296(6), a = 96.99 (3), β=112.47(2), γ= 102.78(2)°, V= 1865(1)~3, D_c= 1.67 g /cm~3, μ= 48.0 cm~(-1), F(000) = 924, Z = 2 (dimers).The molecule is a dimer consisting of two Cp'_2 ErCl species bridged by two Cl atoms. The centralmetal atom Er is coordinated to two Cp' rings and two bridging chlorine atoms forming a pseudo-tetrahedron. All these complexes are soluble in THF, DME, Et_2O, toluene and hexane.  相似文献   

8.
The partially-oxidized TPP[M(Pc)L(2)](2) molecular conductors exhibit variable electronic and magnetic transport bulk materials properties due to central metal and axial ligand molecular modifications. The controllable electrical conductivity and giant negative magnetoresistance can be mainly attributable to the varying ligand field energy and physical bulkiness of the axial ligands which cause modulation in the intra-molecular π-d (Pc-M) and inter-molecular π-π (Pc-Pc) interactions in the TPP[M(Pc)L(2)](2) system, respectively. Characterization of the electronic conduction band utilizing one-dimensional (1-D) tight-binding approximation from infrared reflectance and thermoelectric power profile reveal consistent band widths of 0.43 eV-0.62 eV for the Co series (L = Br < Cl < CN) and 0.44-0.56 eV for the Fe series (L = Br < Cl < CN). The fixed band width suggests that stable electron conduction bands (transport pathway) can be constructed which can withstand the molecular π-d interaction modifications that severely alter the bulk electronic and magnetic materials properties of the TPP[M(Pc)L(2)](2) molecular conductors.  相似文献   

9.
<正> The title compounds have been synthesized and characterized by x-ray analysis. They are isomorphous, belonging to trigonal space group R3m,with crystallo-graphic parameters; (1)α =b =c= 13. 713(5) A ;α= β=γ=83. 66(3)°;V = 2535A3;Z = 2;DC=1. 80gcm-3;F(000) = 1358;M= 1373. 23;(2)α= b = c=13. 687(2) A;α = β = γ = 84. 27(1)°/;V = 2528. 0A3;Z = 2; Dc = 1. 81gcm-3; F (000)= 1362; M = 1377. 23;(3)α = b=c=13. 671(6) A ;α = β = γ=84. 12(3)°;V=2518A3;Z=2;DC = 1. 82 gcm-3;F(000)= 1364;Mr= 1376. 99.The structure of comp ound 2 has been determined with the final R= 0. 061 for 845 reflections with I≥3σ(Ⅰ).The three metal atoms are crystallographically equivalent because of the arbitrariness of orientation of the molecules,and in the sense of crystallography the molecule Fc2CoO(O2CCCl3)6(THF)3 is of C3vsymmetry with centered oxygen atom on the 3-fold axis. The atoms M,C(1~4),C1(1) and O(1) lie on the mirror. Three CC13 groups on one side the Fe2CoO plane and three terminal THF ligands are dynamically  相似文献   

10.
合成了一种新型的配合物{[Cu(Phen)(Nap)_2]_2·(EtOH)_2·(H_2O)_2}(Phen=1,10-菲咯啉,Nap=1-萘甲酸,EtOH=乙醇)。通过元素分析、红外光谱、热重等测试技术对其进行了表征,同时用X射线单晶衍射确定了其晶体结构,其配合物为双核铜结构。利用循环伏安法和发射光谱研究了该配合物的电化学和发光性能;采用紫外光谱和荧光光谱法研究了配合物与小牛胸腺DNA(ct-DNA)的相互作用。结果表明,配合物为不可逆氧化还原过程,其荧光发射光谱为416 nm,与小牛胸腺DNA(ct-DNA)以沟面结合方式相互作用,配合物结合常数Kb1=4.68×10~3L/mol。  相似文献   

11.
The coupled cluster singles and doubles method with perturbative treatment of triple excitations is applied to calculate the potentials of M(z)-X complexes (M = Cu, Ag, and Au; X = He, Ne, and Ar; and z = ±1). The bond functions and the basis set superposition errors are considered to obtain accurate interaction energies. The potential energy curves of all complexes are obtained. The vibrational energy levels and the spectroscopic parameters for these complexes are determined. The analytical potential energy functions are also fitted based on the potential energies.  相似文献   

12.
氧心羧桥三核物通式为[M_3O(RCOO)_6L_3]~(n+)(n=1,0)虽然它在三十年代就已合成出来,但是引起人们广泛兴趣的还是近年来发现的它所具有的特殊稳定性和不寻常的物理化学性质。我们测定了不同M~(2+)离子,两种羧桥的铁系列异三核标题簇合物的晶体结构和有关物理性质。该类型化合物的结构可以看成由共享μ_3-O顶点的三个金属离子的配位八面体组  相似文献   

13.
<正> The title crystal structures have been determined by X-ray diffraction. They crystallize in the monoclinic, space group P21/n, Z=4 with diaensions a= 12.388(1), b= 7.140(1), c= 14.302(1) A,β=90.65(1)° for compound Ⅰ, and a=12.987(2), b= 7.190(1), c=13.284(2) A,β=92.40(2)° for compound Ⅱ. The structures were solved by direct methods, and refined by full matrix least-squares to consistence factors R=0.026 for Ⅰ and R=0.031 for Ⅱ.  相似文献   

14.
The synthesis, IR spectra, and the temperatures of the transition into a ferromagnetic state (T c) of layered ferromagnetics [R3RX[MCr(C2O4)3 (M = Mn, Fe, Co, Cu, and Ni) with the [Ph3BuP]+, [Bu3RN]+ (R = Pr, Et, and Me) cations capable of subsequently changing the distances between metallooxalate layers have been considered. The temperatureT c has been found to be independent of the size of the organic cation. It is believed that the determining factors in the transition to a ferromagnetic state are exchange interactions inside the metallooxalate layer.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 2327–2330, September, 1996.  相似文献   

15.
采用密度泛函理论(DFT)的B3LYP方法, 在6-31G**和Lanl2dz水平上分别对(MN)nHm(M=Ga, In; n=1-4; m=1, 2)进行了优化和振动频率计算. 得到了上述团簇的最稳定构型、H原子的结合能以及它们的能隙. 结果表明, (MN)nH(M=Ga, In; n=1-4)的基态构型均为双重态, (MN)nH2(M=Ga, In; n=1-4)的基态构型均为单重态; 当氢的个数为1时, 加在N原子上比加在M(M=Ga, In)原子上稳定, 如有N3单元, 那么加在N3单元两侧的构型是相同的, 且它是最稳定的; 当氢的个数为2时, 除n=1外, 分别加在两个N原子上的构型是最稳定的, 如有N3单元, 那么分别加在N3单元分离最远的两个N原子的构型是最稳定的. GaNH、(GaN)3H 和InNH的结合能和能隙都很大, 说明这些团簇都有很高的稳定性.  相似文献   

16.
Molecular structure and properties of La and Lu tetrahalide ions LnX 4 ) are studied by the configuration interaction singles-and-doubles method augmented with quadruple excitation correction (CISD+Q) and by the fourth-order Möller-Plesset perturbation theory with account for single, double, triple, and quadruple excitations (SDTQ-MP4). The atomic inner shells are described by Stevens relativistic effective core potentials. Valence basis sets are augmented with diffuse s-, p-, and polarization d-, f-, and g-functions. The equilibrium configuration of nuclei in LnX 4 ions was found to be tetrahedral. The equilibrium internuclear distances, quadratic force constants, vibrational frequencies, and IR intensities of LnX 4 ions are compared with the corresponding parameters of La and Lu trihalide molecules (LnX3), calculated within the same approximations. Regularities in the behavior of molecular parameters on going along the LnF 4 LnCl 4 LnBr 4 LnI 4 series and from La compounds to Lu compounds are revealed. Heights of the energy barriers to the LnX 4 inversion through the square planar structures (T d D 4h T d ) are evaluated: 100–110 and 130–150 kJ/mol for LaX 4 and LuX 4 , respectively. Enthalpies of dissociation reactions LnX 4 LnX3+X are calculated and the results obtained are compared with the available experimental data.Translated from Koordinatsionnaya Khimiya, Vol. 31, No. 3, 2005, pp. 218–228.Original Russian Text Copyright © 2005 by Solomonik, Smirnov, Mileyev.This revised version was published online in April 2005 with a corrected cover date.This revised version was published online in April 2005 with a corrected cover date.  相似文献   

17.
A series of 1D nickel(Ⅱ)/zinc(Ⅱ)-lanthanide(Ⅲ) coordination polymers, [M(μ-L)2Ln(NO3)3]n· solvents (HL =bis(2-pyridylcarbonyl)amine; M = Ni, Ln = Gd (1 · NiGd), Tb (2· NiTb), Dy (3· NiDy), Ho (4· NiHo), Y (5· NiY);M = Zn, Ln =Gd (6· ZnGd), Tb (7· ZnTb), Dy (8· ZnDy), Ho (9· ZnHo); solvents = H2O or H2O-ethanol), was synthesized and characterized. All of the complexes are isostructural at 293 K and crystallize in the orthorhombic space group Fddd. Magnetic measurements were performed on 1-9, where weak ferromagnetic interaction is found in 1 · NiGd, ferromagnetic interaction in 2·NiTb and 3·NiDy, and antiferromagnetic interaction in 4· NiHo. A remarkable dc magnetic field dependence of ac susceptibilities was found in this series of complexes.  相似文献   

18.
半导体纳米晶具有独特的量子限域效应以及新颖的尺寸和形貌依赖特性,已被证实是在低成本高性能光伏器件、光致及电致发光二极管、生物成像、光催化等领域非常具有潜力的新型材料.其中,II-VI族与I-III-VI族半导体纳米晶由于其优异的性能在过去的数十年中引起了广泛的关注.过去数十年对于II-VI族半导体纳米晶的研究已经十分成熟,然而几乎所有的传统II-VI族半导体纳米晶都含有对环境有害的元素,对人体和环境造成不可逆转的伤害,从而限制了II-VI族半导体纳米晶的进一步应用.与二元II-VI族纳米晶相比,大部分三元I-III-VI族纳米晶不含镉和铅等重金属元素,因而具有低毒性的特点,并且其带隙窄、吸光收系数大、斯托克斯位移大、自吸收小以及发光波长在近红外区,所以有望使其成为新一代荧光纳米晶材料.例如,CuInS_2的带隙为1.53 eV,与太阳光谱匹配且其吸光系数较大,在10.5cm.~1左右,从而使其成为制备太阳能电池的一种优秀材料.另一方面,I-III-VI族纳米晶在可见光和近红外范围内呈现与尺寸相关的发光,它们的荧光量子产率在包覆ZnS壳后可超过50%,因而在照明,显示和生物成像领域具广泛应用的潜力.水溶性的I-III-VI族量子点粒径尺寸可以小于10 nm,可以减小纳米颗粒通过肾清除的淘汰率,并且具有高荧光性能和耐光性的特点,因此成为进行生物成像工作的优秀材料.与此同时,I-III-VI族纳米晶在光催化领域也展现了巨大的发展前景.本综述主要关注I-III-VI族纳米晶的合成,性质及应用.首先,我们概述了不同的化学合成方法,并列举讨论了一些经典的工作,根据纳米晶的种类分类统计了主要合成方法、形貌及尺寸.第二部分,我们讨论了它们的光物理和电子特性,解释了纳米晶的"donor-acceptor pair"(DAP)结合机理,概述了I-III-VI族纳米晶的磁光现象.接下来,我们概述了I-III-VI族纳米晶主要的应用领域,着重总结了在太阳能电池领域、半导体发光二极管领域、生物成像领域以及光催化制氢领域的研究进展.最后,我们会讨论半导体纳米晶的应用前景,以及它的机遇和挑战.  相似文献   

19.
A series of 1D nickel(II)/zinc(II)-lanthanide(III) coordination polymers, [M(μ-L)2Ln(NO3)3]n·solvents (HL = bis(2-pyridylcarbonyl)amine; M = Ni, Ln = Gd (1·NiGd), Tb (2·NiTb), Dy (3·NiDy), Ho (4·NiHo), Y (5·NiY); M = Zn, Ln = Gd (6·ZnGd), Tb (7·ZnTb), Dy (8·ZnDy), Ho (9·ZnHo); solvents = H2O or H2O-ethanol), was synthesized and characterized. All of the complexes are isostructural at 293 K and crystallize in the orthorhombic space group Fddd. Magnetic measurements were performed on 1―9, where weak ferromagnetic interaction is found in 1·NiGd, ferromagnetic interaction in 2·NiTb and 3·NiDy, and antiferromagnetic interaction in 4·NiHo. A remarkable dc magnetic field dependence of ac susceptibilities was found in this series of complexes.  相似文献   

20.
AFacileSynthesisof(-)-5_αH,7β,10_α-Eudesmane-3,11-diene¥NingZOU;DongLiangCHENG;XinFuPAN;YaoZuCHEN(DepartmentofChemistry,Lanzho...  相似文献   

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