稀土元素(Ce/Nd/Eu/Gd)与N共掺金红石相TiO2的第一性原理研究

基于密度泛函理论的第一性原理平面波超软赝势计算方法,计算分析了纯金红石相TiO2,Ce、Nd、Eu和Gd四种稀土元素单掺杂金红石相TiO2,以及与N共掺金红石相TiO2的晶体结构、电子结构和光学性质.由掺杂前后的结果分析发现,掺杂后晶胞膨胀,晶格发生畸变;费米能级上移进入导带,导带底部引入杂质能级,提高了掺杂体系的电导率和对可见光的响应;光学性质、介电函数和吸收谱掺杂体系峰值比纯TiO2小,反射谱和能量损耗谱出现红移现象.     

Ca掺杂ZnO氧化物的电子结构与电性能研究

基于密度泛函理论广义梯度近似第一性原理计算的方法,系统研究了Ca掺杂ZnO氧化物的晶格结构和电子结构,在此基础上分析了其电学性能.结果表明,Ca掺杂ZnO晶胞减小.Ca掺杂氧化物仍为直接带隙半导体材料,带宽达1.5 eV.掺杂体系费米能级附近的能带主要由Cas态、Cap态、Znp态和Op态电子构成,其中p态电子对价带态贡献最大,且Cas态、Znp态和Op态电子之间存在着更强的相互作用.Ca掺杂ZnO氧化物费米能级EF附近载流子浓度增加,运动速度减小,有效质量增加,导电机构为Cas态、Znp态和Op态电子在价带与导带的跃迁,具有更高的电导率,较高的Seebeck系数和综合电性能.     

Hf/Ta/W单掺锐钛矿相TiO2的电子结构和光学性质的第一性原理研究

运用第一性原理赝势方法计算过渡金属X(Hf、Ta、W)单掺锐钛矿相TiO2后的电子能带结构、态密度和光学性质.计算结果表明,X掺锐钛矿相TiO2,使得掺杂后体系的体积增大,并随着X掺杂浓度的增加而增大;掺杂体系的禁带宽度都比纯TiO2的要小;由能带图可知,Ta、W单掺后,费米能级进入导带,说明这两种单掺体系属于N型半导体;随着不同浓度Hf、Ta、W的掺入,发现吸收光谱都发生了不同程度的红移,其中Ta、W掺杂体系的光响应范围覆盖了整个可见光区域,对比所有掺杂体系发现Ti0.9375 W0.0833 O2在可见光区域的光响应能力最强,这些现象说明X的掺入大大提升了TiO2光催化能力.     

S与Hf/Ta/W掺杂锐钛矿相TiO2电子结构和 光学性质的第一性原理研究

运用第一性原理密度泛函理论,计算了S单掺及S和过渡金属X(Hf、Ta、W)共掺锐钛矿相TiO2后的电子结构和光学性质.计算结果表明,S单掺及S和X(Hf、Ta、W)共掺杂锐钛矿TiO2后,带隙变窄,表明掺杂后的体系导电性能增强,其中Ta、W与S共掺后,费米能级穿过导带,表现出n型半导体特征;光学性质结果表明:掺杂后各体系的吸收光谱吸收带边均发生红移,S-Ta共掺和S-W共掺体系红移程度最大,并且在可见光区域出现吸收峰,S-W共掺体系的吸收峰最大,说明了该体系的光催化功能较强.各掺杂体系的反射率主峰均向低能方向移动,共掺移动幅度更大,且S-W共掺体系的反射系数在可见光区最大.各共掺体系的静态折射率依次增大,其中S-Hf共掺体系静态折射率在各体系中最小.     

Mg/Cd共掺杂ZnO电子结构与光学性质的第一性原理研究

采用基于密度泛函理论的第一性原理平面波超软赝势法,研究了Mg/Cd(不同的Cd浓度)共掺杂ZnO的电子结构和光学性质.研究表明:Mg/Cd共掺杂ZnO,体系的晶胞尺寸变大,但结构稳定.当Mg/Cd为1:1时,吸收边略微发生蓝移.随Cd的掺杂浓度增加,导带部分逐渐下移,禁带宽度变窄,出现红移现象.除此之外体系的吸收率和反射率也减小.说明Mg/Cd共掺杂ZnO,不仅使得体系光学谱丰富,而且透射性增强.这对实验中制备出高透射率的材料具有一定的指导意义.     

Mg掺杂浓度对GaN电子结构和光学性质的影响

基于密度泛函理论的第一性原理,分析了Mg掺杂浓度对GaN晶格参数、能带结构、电子态密度和光学性质的影响.研究表明:Mg掺杂GaN体系,晶格常数增大,禁带宽度增加,而且禁带宽度随着Mg含量的增加而增加,同时N2p和Mg2p态电子轨道的相互杂化,从而在费米能级附近引入受主能级,随着Mg含量的增加,费米能级进入价带的位置加深,同时Mg掺杂浓度越高,价带和导带带宽越窄.掺Mg后在介电函数和光学吸收谱的低能区和高能区均出现了新的介电峰,这些峰的出现和禁带中的杂质能级到导带底的跃迁有关,由于带隙的增加使介电峰向高能量方向发生偏移.     

S-La共掺杂ZnO性能的第一性原理研究

采用基于广义梯度近似的第一性原理方法,研究了纯ZnO、S单掺、La单掺和S-La共掺ZnO的能带结构、态密度和光学性质.S单掺ZnO后,价带和导带同时向低能量转移,导致带隙减小.La单掺ZnO后在导带底产生杂质能级使得带隙减小.S-La共掺ZnO导致La的局部化减弱,表明La形成的施主能级由于S的3 p态的影响变得更浅...     

Co掺杂对ZnO晶体中光生电子瞬态过程的影响

采用气相反应制备了ZnO和ZnO∶Co微晶,并通过热释光研究了材料中的电子陷阱能级(施主能级),采用微波介电谱研究了材料的光生电子瞬态过程.发现纯ZnO热释光谱有两个峰,分别为-183 ℃和-127 ℃,说明存在两个电子陷阱能级;而ZnO∶Co中热释光信号很弱,只有纯ZnO的十分之一.微波介电谱研究表明,由于电子陷阱对导带电子的驰豫作用,纯ZnO材料导带光电子的衰减为一级指数过程,寿命为802 ns.ZnO∶Co微晶体的最大微波介电谱强度低于纯ZnO晶体的五分之一,电子陷阱密度较小,其光生电子快速衰减,过程仅为10～20 ns.结果说明Co掺杂具有明显的抑制电子陷阱能级生成的作用.     

GGA+U法研究稀土(La、Ce、Pr、Nd)掺杂对ZnO电子结构和光学性质的影响

基于GGA+U的第一性原理方法,分析了La、Ce、Pr、Nd四种元素掺杂的ZnO结构,对晶体的结构、电子结构和光学性质进行了对比分析.由键布局分析可知,掺杂体系Zn-O键共价性的强弱与杂质掺入原子的序数成正比.掺杂后体系的类型仍为直接跃迁,能级整体下移;随着Pr、Nd掺入,出现了杂质能级,这是由稀土元素的4f电子态所导致.在光学性质方面,掺杂体系的吸收系数、静介电常数都比纯ZnO的高,体系的吸收边都向低能方向移动,其中Zn7LaO8的红移程度最高、静介电常数最大,说明其光催化能力和极化能力都最强.     

La掺杂量对ZnO光电性能影响的第一性原理研究

采用密度泛函理论下的平面波超软赝势方法和杂化泛函理论下的模守恒赝势方法,分别计算了未掺杂ZnO和两种La掺杂浓度的ZnO模型,其中对较高La掺杂浓度的计算还设置了两种不同的掺杂位置.结构优化后,首先通过计算形成能、系统总能量和电荷布居值,对掺杂后体系的稳定性进行了分析;而后结合自旋基态能量与自旋电子态密度对掺杂体系的磁性状态进行了说明;最后通过计算得到的电子结构及吸收光谱讨论了La掺杂量对ZnO光电性能的影响.结果表明:随La掺杂量增加,ZnO体系稳定性有所降低;La掺杂ZnO无磁性,电子结构不会受到自旋能级分裂的影响;与纯ZnO相比,La掺杂ZnO的禁带宽度增大,吸收光谱蓝移,然而通过控制La浓度与掺杂方式可以有效增强La-5d与Zn-4s电子态的交换关联作用而减小ZnO的最小光学带隙,提高ZnO对可见光的吸收系数,使光生空穴-电子对有效分离的影响.     

Periodic structure during unidirectional solidification for peritectic Cd–Sn alloys

Unidirectional solidification for the peritectic Sn–1.0, 1.5, 2.0 at% Cd alloys was carried out under temperature gradients of 2.7×10³ K/m for 4 mm diameter specimens, and 5.3×10³ K/m for 2 mm diameter specimens. A banded structure in which the two constituent phases alternatively form perpendicular to the growth direction was observed in the 2 mm diameter specimens. On the other hand, a competitive microstructure was obtained in the 4 mm diameter specimens, in which the two phases interlace and the three-phase junction fluctuated in the radial direction during unidirectional solidification. Formation of the banded structure depended on the specimen diameter, while the transition from the cellular interface to the planar interface was not affected by the specimen diameter. In the high G/V region for peritectic alloys, the growth morphology in which the phases grow side by side is unstable, even if the pulling rate and temperature profile are constant. The banded structure and the competitive structure originate through the same mechanism; this is intrinsic for peritectic alloys with two-phase composition.     

Analysis of the crystal structures of 1,3‐di‐tert‐butyl‐2,3‐dihydro‐1H‐1,3,2‐diazasilol‐2‐ylidene and 1,3‐di‐tert‐butyl‐2,2‐dichloro‐1,3‐diaza‐2‐sila‐4‐cyclopentene

The crystal structures of the title compounds, 1,3‐di‐tert‐butyl‐2,3‐dihydro‐1H‐1,3,2‐diazasilol‐2‐ylidene, C₁₀H₂₀N₂Si ( 1 ) and 1,3‐di‐tert‐butyl‐2,2‐dichloro‐1,3‐diaza‐2‐sila‐4‐cyclopentene, C₁₀H₂₀N₂SiCl2 ( 3 ) were solved and are reported. Compound ( 1 ) crystallized in space group P mmn and each molecule has a mirror plane, which bisects the C‐C backbone of the N‐C‐C‐N framework. Compound ( 1 ) was also found to have a 2‐fold twin component. In compound ( 3 ) the space group P 2₁/m results with the mirror plane passing through the N‐C‐C‐N backbone. We compare these structures with the gas phase determination previously reported for ( 1 ) and the incomplete single crystal data for ( 3 ). (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Synthesis and Crystal Structure of Mixed-valence Hexanuclear Manganase Oxide Complex,Hexakis(μ<Subscript>2</Subscript>-pivalato)-tetrakis(μ<Subscript>3</Subscript>-pivalato)-mono(pyridine)-tris(pivalic acid)-bis(μ<Subscript>4</Subscript>-oxo)dimanganese(III) tetramanganase(II)

Abstract  The complex, [Mn₆O₂(OOCCMe₃)₁₀(HOOCCMe₃)₃(py)], has a hexanuclear structure with a Mn₆O₂ core. This complex crystallizes in the monoclinic space group P2₁/n with a = 17.757(5) ?, b = 27.413(5) ?, c = 22.348(5) ?, β = 90.233(5)°, V = 9,040(4) ?³ and Z = 4. It contains a [Mn₆O₂]¹⁰⁺ core that can be described as two edge-sharing Mn₄ tetrahedra at the centre of each of which tetrahedron lies a μ₄-O²⁻ ion. All Mn atoms are six-coordinate and possess distorted octahedral geometry. Mn₄ exhibits butterfly arrangement with both μ₄-O atoms on the same side of the molecule. The complex is mixed-valence , and the Mn^III centers are assigned as the two central metal ions bridged by two O²⁻ ions. Index abstract  The complex, [Mn₆O₂(OOCCMe₃)₁₀(HOOCCMe₃)₃(py)], has a hexanuclear structure with a Mn₆O₂ core. This complex crystallizes in the monoclinic space group P2₁/n with a = 17.757(5) ?, b = 27.413(5) ?, c = 22.348(5) ?, β = 90.233(5)°, V = 9040(4) ?³ and Z = 4. It contains a [Mn₆O₂]¹⁰⁺ core that can be described as two edge-sharing Mn₄ tetrahedra at the centre of each of which tetrahedron lies a μ₄-O²⁻ ion. All Mn atoms are six-coordinate and possess distorted octahedral geometry. Mn₄ exhibits butterfly arrangement with both μ₄-O atoms on the same side of the molecule. The complex is mixed-valence , and the Mn^III centers are assigned as the two central metal ions bridged by two O²⁻ ions.      

Crystal Structure Analysis of 3'5' (dichloro phenyl)‐3‐ethyl‐5‐phenyl thio indalo [1,2‐e] imidazolidine

The title compound crystallizes in monoclinic system with space group P2₁ /n. The cell parameters are a = 12.3824(3) Å, b = 8.9255(1) Å, c = 19.9188(4) Å, V = 2181.75(7) ų , α = γ = 90.0° and β = 97.663(1)°. The structure has an indole moiety and an imidazolidine ring connected together. The phenyl sulfonyl group is attached to the indole moiety and the dichlorophenyl ring to the imidazolidine ring. The structure has a C‐H … Cl intra molecular hydrogen bond and C‐H … π type intermolecular interactions.     

Structure Analysis of Methyl‐3,4‐dihydro‐3‐(p‐methylphenyl)‐4‐oxo‐2‐quinazolinyl thiopropionate

The crystal structure of methyl‐3, 4‐dihydro‐3‐(p‐methylphenyl)‐4‐oxo‐2‐quinazolinyl thiopropionate (C₁₉H₁₈N₂O₃S) has been determined by X‐ray diffraction methods. The compound crystallizes in the triclinic space group P with unit cell parameters: a = 9.094(2), b = 9.428(3), c = 10.612(3) Å, α = 94.55(3), β = 95.44(2), γ = 106.75(3)° and Z = 2. The structure has been refined to an R‐value of 0.054 for 2533 observed reflections [F_o > 4σ(F_o)]. The quinazoline moiety and the methyl substituted phenyl ring is almost planar. The dihedral angle between these two moieties is 84.96(8)° . The crystal structure is stabilized by an intermolecular C‐H … O interaction.     

Crystal and Molecular Structure of (9R)‐10,11‐dihydro‐6′‐methoxy‐cinchonan‐9‐ol‐4‐chlorobenzoate hydrochloride

The crystal structure of the title compound has been determined by single crystal X‐ray diffraction methods. C₂₇H₂₉N₂O₃Cl.HCl is one of the cinchona alkaloids. It crystallizes in the space group P2₁2₁2₁ with a = 11.745(3), b = 12.353(6), c = 17.253(6) Å and Z = 4. The structure was refined to a final R value of 0.062 for 2155 observed reflections. The C—N distances are unequal in the quinoline ring system. In quinulidine ring, the bonds around N are more tetrahedral. The spatial arrangement and torsion angles show the open conformation of the molecule. The molecular packing is stabilized by hydrogen bonding.     

The Crystal Structures of O,O‐Dimethylalpinumisoflavone and 5‐O‐Methyl‐4'‐O‐(3‐methyl‐but‐2‐en‐1‐yl)alpinumisoflavone

The petrol extract of the rootbark of Milletia Thonningii obtained by column chromatography afforded sixteen different crystalline samples to be isolated. The crystal structures of two of these compounds, O,O‐Dimethylalpinumisoflavone (I) and 5‐O‐Methyl‐4'‐O‐(3‐methyl‐but‐2‐en‐1‐yl)alpinumisoflavone (II) are being reported here. (II) has two independent molecules in the asymmetric unit and differs from (I) in a longer side chain attached to C(15) of the phenyl ring. The structural features of the three molecules in the title compounds are reported and compared. The derivatives, being subject of this article are the first reported crystal structures where the isoflavone fragment is fused to a further six membered ring that results in a tricyclic ring system. The benzopyrone fragments are planar. The dihedral angles between the benzopyrone fragment and the phenyl ring being 55.38(6)° for (I) and 44.75(15)° /44.64(15)° for the respective independent molecules of (II) are within the range of values observed for similar structures.     

The Crystal and Molecular Structure of 11,12‐dibromo‐ 7,8—benzo‐1,5‐di(p—tolylsulphonyl)‐1,5‐diazacyclononan

The crystal structure of the title compound, C₂₅H₂₆Br₂N₂O₄S₂ was determined by single crystal X‐ray diffraction technique. The crystals are monoclinic, space group C 2/c, with a=20.7142(2) Å b=11.7910(2) Å, c= 10.6735(3) Å, β=98.549(2)°, V=2577.94(9) ų, Z=4. The structure was solved by direct methods and refined by least‐squares methods to a final R=0.046 for 1866 observed reflections with I>2sigma(I). The title compound, displays disordered geometry around the C1 atom located almost on twofold axis. The nine‐membered heterocylic ring is close to the half‐chair conformation. The dihedral angle between phenyl rings is 34.2(1)°.     

双核Cu(Ⅱ)乙二醇双(α-氨基乙基)醚四乙酸配合物的合成、表征及晶体结构

本文采用CuCl_2和乙二醇双(α-氨基乙基)醚四乙酸在甲醇和水溶液中合成了双核铜配合物,通过元素分析、红外光谱对配合物进行了表征,利用X单晶射线衍射仪测定了其结构.结构解析表明,该标题配合物属三斜晶系,空间群C2/c,晶胞参数a=2.0984(10) nm,b=0.7535(3) nm,c=1.3555(6) nm;α=90 °,β=90.8980(10) °,γ=90 °,V=2.1432(16)nm~3,Z=8,Dc=1.783 g.cm~(-3),F(000)=1184,μ=2.059 mm~(-1),最终偏差因子(对I＞2σ(I)的衍射点),R_1 = 0.0216,wR_2=0.0654,对全部衍射点R_1= 0.0249,wR_2=0.0664.在该配合物中,每个配体分别与两个中心金属离子螯合作用.每个铜离子均采用扭曲的三角双锥结构,分别与配体中的一个N原子,末端两个羧基上的氧原子以及两个水分子配位.