Crystal Chemistry of Nanotubes Lattices

Abstract

X-ray diffraction profiles of pristine and hypothetical “intercalated” crystalline bundles of single-wall carbon nanotubes are computed and compared with experiment. The pristine case is complicated by finite size effects, tube diameter dispersion and the cylindrical form factor for uncorrelated tube rotations. Experimental profiles of “doped” samples are not in agreement with simulations based on 2-D ordered sublattices except at very low doping levels.     

Crystal Chemistry of Hydrous Aluminium Arsenate Minerals

Crystallography Reports - The hydrous aluminium arsenate minerals form a small but diverse group of crystal structures. They range from mansfieldite, AlAsO4 ? 2H2O, with isolated Al-centred...     

短程有序双周期非线性光子晶体中宽带级联三次谐波产生的研究

从理论和数值模拟上分析了一种一维短程有序双周期铁电畴结构中宽带级联三次谐波的产生过程.这种短程有序结构是由一系列一定长度的双周期极化铁电畴结构和任意长度的单畴结构交替构成.研究了结构参数对级联三次谐波产生过程中频谱带宽和转换效率的影响.结果表明,通过控制双周期极化结构段的长度可以实现级联频率转换过程中带宽的调节,而级联三次谐波的转换效率可以通过增加谐波和晶体的作用长度来实现.     

一种翡翠仿制品-透辉石微晶玻璃显微结构及晶体化学特征的研究

利用偏光显微镜、电子探针仪及X射线粉晶衍射仪,对一种翡翠的仿制品-人造透辉石微晶玻璃的显微结构、析晶特征、化学成分及物相组成进行了研究.该微晶玻璃外观具有明显的放射状晶花,偏光显微镜下观察及BSE图像反映出透辉石微晶玻璃具有显微斑状结构,且含特征的骸晶.电子探针测试得到该材料内玻璃质基质、主晶相透辉石及少量石英的化学成分,其中透辉石内的镍含量明显高于天然翡翠.X射线粉晶衍射分析确定其主要物相为透辉石和玻璃质,与天然翡翠以硬玉、纳铬辉石等为主要矿物组成不同.     

X-Ray Crystal Structure and Photo Chemistry of N-Methyl-N-(1-phenylvinyl)benzamide

Abstract  

N-methyl-N-(1-phenylvinyl)benzamide (I) has empirical formula C₁₆H₁₅NO, crystallizes in the monoclinic space group, P21/n, with unit cell parameters a = 8.9101(2) ?, b = 15.1416(4) ?, c = 9.7737(2) ?, α = 90°, β = 109.3320(10)°, γ = 90°, Z = 4. Interestingly, the Compound (I) undergoes photocyclization upon irradiation of light to give two cyclic lactams (A and B) below 3100 ?. Compound (I) can be cyclized at either of two equivalent ortho positions. The mechanism for formation of lactam A may involve electrocyclic ring closure reaction upon irradiation of light to give six-membered cyclic zwitterionic intermediate. The ring proton rearranges via [1, 5]-H shift to give isomerized product A. The minor photoproduct B is supposed to be formed via photocyclization process followed by a loss of proton and the tautomerized product undergoes oxidation for the revival of aromaticity.     

Crystal Chemistry of 1:1 Molecular Complexes of Carbamate Salts Formed by Slow Aerial Carbonation of Amines

Abstract  Amines do have rare tendency to undergo aerial carbonation to form carbamic acid. Four different 1:1 molecular complex of carbamate salts reported herein obtained by the aerial carbonation of cyclic amines. X-ray crystal structures show a systematic change in the molecular structure did bring some gradual supramolecular change from one structural motif to another. Index Abstract  Amines do have rare tendency to undergo aerial carbonation to form carbamic acid. Four different 1:1 molecular complexes of carbamate salts reported herein obtained by the aerial carbonation of cyclic amines. X-ray crystal structures show a systematic change in the molecular structure did bring some gradual supramolecular change from one structural motif to another.      

有序纳米半导体量子点的自组织生长

纳米半导体量子点以其所具有的新颖光电性质与输运特性,正在各类量子功能器件中获得成功应用.作为纳米量子点的一种主要制备工艺,自组织生长技术正在受到人们的普遍重视.而如何实现具有尺寸与密度可控纳米量子点的自组织生长,更为材料物理学家们所广泛关注.因为这是由自组织方法形成的量子点最终能否器件实用化的关键.本文简要介绍了有序纳米量子点的自组织生长及其新近研究进展.     

具有梯度结构的蛋白石光子晶体的制备

具有梯度结构的蛋白石光子晶体具有独特的光学性能。本文通过垂直沉积法和电场诱导沉积等方法共同作用将具有不同直径的聚苯乙烯(Polystyrene)胶体微球逐层组装在一起,制备出具有梯度周期尺寸变化的蛋白石结构。     

A Novel Sodium and Chromium Borophosphate Na{Cr[BP2O7(OH)3]}: Synthesis,Crystal Structure,Hydrogen Bonding,and Comparative Crystal Chemistry

Crystallography Reports - A novel sodium and chromium borophosphate, obtained by hydrothermal synthesis in the Na2O–P2O5–B2O3–Cr2O3–Н2О system, has been...     

Photonic Band Effect in Ordered Polystyrene Particle Layers

Abstract

Quasi two-dimensional (2D) photonic band structures have been investigated on ordered polystyrene particle layers by means of polarized transmission spectra for oblique incidence of light. The results are discussed in terms of quasi-2D photonic band effect.     

晶体对热辐射的吸收对晶体生长的影响

本文综述了晶体对熔体热辐射吸收对晶体生长的影响,包括对热腔热耗散的影响;对晶体生长温度时间特性的影响;对液流形态和固液界面形状的影响;对晶体界面反转的影响;对晶体中温度分布和应力分布的影响.     

绿柱石晶体的水热法生长及特征研究

采用温差水热法,以分析纯的Al(OH)3和BeO以及无色纯净的石英为原材料,球形和//s(1121)的片状无色绿柱石为籽晶,在复杂的盐酸混合溶液中生长了无色透明的绿柱石晶体.利用双圈反射测角仪、电子探针、X射线衍射仪和红外光谱仪等仪器,对合成绿柱石晶体的形态、成分及晶体结构进行了详细的研究.结果表明,合成的绿柱石晶体为六方短柱状,主要发育平行双面c{0001}、六方柱m{1010}、a{1120}和六方双锥p{1011}四种单形.合成的绿柱石晶体的成分中(Na2O+ K2O)的质量分数约为0.59;,且c0/a0值为0.9988,可归属于"正常"绿柱石向"四面体"绿柱石的过渡范畴.在中性或弱碱性环境体系中,通过调整绿柱石中各成分的百分含量,有望在更低的温度、压力条件下合成出高质量的板柱状绿柱石晶体.     

Ordered structures based on self-organized Au and CdSe nanoparticles

Methods for obtaining cadmium selenide and gold nanoparticles have been developed. The sizes of the nanoparticles are determined and the morphology, structure, and chemical composition of these nanoparticles and their ensembles are studied by a complex of structural methods: electron diffraction, X-ray diffraction, energy-dispersive X-ray analysis, high-resolution transmission electron microscopy, and small-angle X-ray scattering. Gold nanoparticles are mainly spherical and have an average size of 10 nm. They are single-phase and have an fcc crystal structure. Samples of synthesized CdSe nanoparticles contain monodisperse spherical particles 12 nm in size with a wurtzite structure. The deposition of nanoparticles on a carbon substrate is accompanied by their self-organization into a closely packed two-dimensional structure with a pronounced texture in which all nanoparticles are oriented in the [001] direction perpendicularly to the carbon substrate plane.     

无序化对有序铁铝金属间化合物磁性的影响

在平衡态时,化学计量比成份Fe3Al具有D03超结构,并表现出铁磁性,平均每个Fe原子的磁矩是1.7μB,而具有B2超结构的FeAl却是无磁的.利用快速凝固、冷加工处理、溅射和机械合金化等非平衡加工技术可以使D03-Fe3Al和B2-FeAl等有序铁铝金属间化合物相无序化.本文利用固体与分子经验电子理论(EET)和Jaccarino-Walker模型对铁铝金属间化合物的磁性进行了计算,研究了无序化对Fe-Al有序相磁性的影响.结果表明:完全无序的Fe75Al25和Fe50Al50,每个Fe原子的平均磁矩分别是2.01μB、1.41μB,铁铝金属间化合物的磁性可以通过无序化提高.     

Novel Polyoxovanadate K<Subscript>2</Subscript>ZnV<Subscript>5</Subscript>O<Subscript>14</Subscript>: Crystal Structure and Peculiarities of Crystal Chemistry

A novel structure type has been established as a result of studying a non-merohedral microtwin of polyoxovanadate (K₂ZnV₅O₁₄) by X-ray diffractometry (R = 0.0595). The new compound, synthesized under hydrothermal conditions in the ZnCl₂–K₂CO₃–V₂O₅–H₂O system, is characterized as follows: a = 8.066(5) Å, b = 8.117(5) Å, c = 9.236(5) Å, β = 105.287(5)°, sp. P2₁/m, Z = 2, ρ_calcd = 3.54 g/cm³. Edge-shared five-core “clusters” consisting of vanadium octahedra, between which ZnO₄ tetrahedra (sharing vertices with octahedra) are located, form two-dimensional two-layer anion packets of the (ZnV₅O₁₄)^2– composition, alternating along the c axis with layers of potassium atoms. Structural peculiarities determine the morphology and color of new-phase crystals.     

高抗灰迹KTP晶体生长与性能研究

采用顶部熔盐籽晶法生长了具有高抗灰迹性能的KTiOPO4(HGTR-KTP)晶体,并对其透过光谱、光学均匀性、相位匹配角、抗激光损伤阈值等性能进行了表征和测试,与普通KTP晶体的对比和大功率激光实验表明该晶体具有高的抗灰迹性能。     

Crystal Growth from Silica Gels and Single Crystal Structure of Bariumchromate

Rhombic single crystals of bariumchromate were grown in silica gels up to 1.5 mm in size. The influence of the initial pH-value of the gel and the kind and concentration of reactants are studied. The crystal structure has been determined. The compound crystallizes in space group Pnma, with cell dimensions a = 9.113(4) Å, b = 5.528(3) Å, c = 7.336(4) Å and Z = 4. The structure was refined to R = 0.062 on the basis of 364 reflections. Every barium atome, centered in a distorted archimedian antiprism, is coordinated to 8 oxygen atoms each belonging to a chromate tetrahedron. Interatomic distances and bond angles were calculated.     

KDP晶体缺陷对生长应力分布的影响

本文采用有限元法分析了不同尺寸、形状的晶体缺陷对大口径KDP晶体生长应力分布的影响.结果表明,晶体中的缺陷导致了晶体内部应力集中,且应力集中程度与缺陷尺寸、晶体生长尺寸呈反向变化,而最大主应力与缺陷尺寸、晶体生长尺寸呈正向变化.当缺陷含有棱边或尖角时,应力集中程度和最大主应力值都明显增加.由于KDP晶体易脆性开裂,随着最大主应力值的增大,开裂机率也增大.     

不同籽晶对多晶硅晶体生长的影响

通过在坩埚底部铺设籽晶来控制形核的同步性,获得均一等大的硅晶粒,实验采用铺设硅粉、颗粒料、碎硅片三种籽晶来诱导硅晶体生长,结果表明硅粉籽晶生长硅晶体晶粒均匀性最好.采用硅粉籽晶所生产硅锭效率比碎硅片籽晶高0.3;.