共查询到19条相似文献,搜索用时 78 毫秒
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2011年诺贝尔化学奖授予以色列科学家达尼埃尔.谢赫特曼)Daniel Shechtman),以表彰他发现准晶体)Quasicrystals)的贡献。准晶体与传统晶体不同,它具有5次旋转轴的长程有序结构,它的发现和研究具有重要学术和应用价值。 相似文献
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MB25镁合金中的准晶体与晶体相的研究 总被引:3,自引:0,他引:3
利用透射电子显微术(TEM)及能谱仪微区成分分析(EDS)技术,对含有稀土元素的铸态Mg-Zn-Zr-Y系高强镁合金MB25中的稀土相鉴定发现,在铸态合金的晶界上存在准晶相,其电子衍射谱显示出5-3-2次对称的特点,为二十面体准晶相。在与准晶相连区域发现一种MgZn_2型的Laves相,其点阵常数为a=0.542nm,C=0.873nm。 相似文献
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采用五层阶梯形模具冷却方法在Mg68Zn29Y3合金中制备了二十面体准晶相(I相)。通过扫描电镜、能谱分析仪和透射电子显微分析技术,观察了合金凝固组织和准晶相的形貌,并确定了准晶相成分及结构。结果表明:Mg68Zn29Y3三元合金在普通凝固-阶梯模冷却过程中,冷却速度对准晶相形貌、数量、大小和分布存在较为显著的影响;随着冷速的降低,准晶相的生长方式由细小弥散演变为粗大碎化,准晶晶粒尺寸由20μm逐渐长大至100μm以上;准晶相通过包晶反应形核、长大;合金凝固组织为MgZn+α-Mg+Zn60Mg30Y10。 相似文献
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分子动力学模拟纳米晶体银的结构和性能 总被引:1,自引:0,他引:1
通过分子动力学方法,采用以局域密度(LDA)近似和二阶动量矩(SMA)近似为基础的多体势函数,模拟了纳米面心立方晶体银的结构,对模拟的结果进了不同尺寸的纳米晶体的能量分布,弹性常数,表面能及熔点等计算,并与相应的实验结果进行了比较,结果表明采用此多体势函数模拟纳米晶体的结构和性能,比用其它势函数更精确,与实验结果更吻合。 相似文献
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2011年诺贝尔化学奖颁发给了以色列科学家DanShechtman,以表彰他在准晶发现上的突出贡献。本文简单介绍准晶发现的重要意义及其结构的描述方式。 相似文献
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Charlotte M. Wentz Kätchen K. Lachmayr Dr. Esther H. R. Tsai Prof. Dr. Lawrence R. Sita 《Angewandte Chemie (International ed. in English)》2023,62(23):e202302739
Experimental results are presented that serve to lower the barrier for developing the science and technology of non-classical thermotropic glycolipid mesophases, which now include dodecagonal quasicrystal (DDQC) and Frank–Kasper (FK) A15 and σ mesophases that can be produced under mild conditions from a versatile class of sugar-polyolefin conjugates. By employing “alloys” comprised of mono- and disaccharide-polyolefin conjugates, and optionally with vitamin E as a small molecule phase modulator, we report the spontaneous formation of stable A15 mesophases at ambient temperature. We further document a rich thermotropic phase map that includes DDQC, A15, and σ mesophases of tunable periodicity that are connected through rapid thermotropic phase transitions as a function of increasing temperature in the order: liquid-like packing (LLP)→DDQC → A15→σ→ disorder. This first direct observation of a rapid thermotropic A15→σ phase transition provides support for a diffusionless martensitic process proceeding through strain-induced introduction of planar defects into the A15 lattice. 相似文献
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Twenty years ago our journal Structural Chemistry was founded with the primary purpose of providing a quality venue for reports that present the result of complex studies
of chemical and biological systems and in the field of materials science, using diverse physical and computational techniques
simultaneously and in a concerted way and that are concerned with the chemical, biological, and physical implications of the
findings. A sampler of contributions witnesses the fulfillment of this goal and points justified expectations of a bright
future for our publication. 相似文献
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超分子结构化学 总被引:5,自引:0,他引:5
超分子 (supramolecule)通常是指由两种或两种以上分子依靠分子间相互作用结合在一起 ,组装成复杂的、有组织的聚集体 ,并保持一定的完整性 ,使其具有明确的微观结构和宏观特性。由分子到超分子和分子间相互作用的关系 ,正如由原子到分子和共价键的关系一样。 1 987年 ,诺贝尔化学奖授予C .Pedersen(佩德森 )、J M .Lehn(莱恩 )和D .Cram(克拉姆 )等在超分子化学领域中的奠基工作 :佩德森发现冠醚化合物 ,莱恩发现穴醚化合物并提出超分子概念 ,克拉姆是主客体化学的先驱者[1~ 3] 。此后 ,作为化学的… 相似文献
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碳和硅结构化学的比较 总被引:1,自引:0,他引:1
碳和硅是元素周期表第14族的前两个元素,它们在化学中占有极其重要的地位。碳统治着有机化学,有机化合物的定义是一切含有C—C键的化合物。硅统治着无机化学,硅在地壳中的含量按40km厚度的地壳计,约占地壳质量的28%,在地壳的所有元素中,硅仅次于氧而居第二位。硅和氧以及其他元素一起结合形成硅酸盐,硅酸盐化合物占地壳质量的80%以上,单是长石一类硅酸盐矿物就占地壳质量的一半。为什么这两个元素有如此独特的能力?关键在于这两个元素的原子能各自形成独特的化学键。1碳和硅化学键的比较在基态时,碳和硅的电子组态分别为:C:[He]2s22p2;Si:… 相似文献
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Dr. Phil Liebing Dr. Cody Ross Pitts Marc Reimann Dr. Nils Trapp Dr. David Rombach Dustin Bornemann Prof. Dr. Martin Kaupp Prof. Dr. Antonio Togni 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(19):6086-6093
The analysis of crystal structures of SF5- or SF4-containing molecules revealed that these groups are often surrounded by hydrogen or other fluorine atoms. Even though fluorine prefers F⋅⋅⋅H over F⋅⋅⋅F contacts, the latter appeared to be important in many compounds. In a significant number of datasets, the closest F⋅⋅⋅F contacts are below 95 % of the van der Waals distance of two F atoms. Moreover, a number of repeating structural motifs formed by contacts between SF5 groups was identified, including different supramolecular dimers and infinite chains. Among SF4-containing molecules, the study focused on SF4Cl compounds, including the first solid-state structure analyses of these reactive species. Additionally, electrostatic potential surfaces of a series of Ph-SF5 derivatives were calculated, pointing out the substituent influence on the ability of F⋅⋅⋅X contact formation (X=F or other electronegative atom). Interaction energies were calculated for different dimeric arrangements of Ph-SF5, which were extracted from experimental crystal structure determinations. 相似文献
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Kerstin Scheurell René König Prof. Dr. Sergey I. Troyanov Prof. Dr. Erhard Kemnitz 《无机化学与普通化学杂志》2012,638(9):1265-1273
Magnesium acetate solvates, Mg(OAc)2 · nL, and their hydrates were prepared by crystallization of Mg(OAc)2 · 4H2O or Mg(OAc)2 from different solvents (L = MeOH, EtOH, HOAc). Anhydrous Mg(OAc)2 was obtained by thermal dehydration of the tetrahydrate at 150 °C. X‐ray single crystal diffraction mostly with the use of synchrotron radiation allowed the structure determination of Mg(OAc)2(H2O)3(EtOH) ( I ), Mg(OAc)2(HOAc)2(H2O)2 ( II ), Mg3(OAc)6(MeOH)6 ( III ), Mg3(OAc)6(HOAc)2(H2O)2 · 2HOAc ( IV ), Mg(OAc)2(HOAc) · 1.8(HOAc) ( V ), Mg(OAc)2 · H2O ( VI ), [Mg3(OAc)6(EtOH)2] · 2EtOH ( VII ), and Mg(OAc)2 ( VIII ). Structural data were discussed in terms of the number of neutral O‐donor ligands per magnesium atom, coordination environment of magnesium atoms, structural functions of acetate groups, and hydrogen bonding systems. 相似文献
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1INTRoDUCTIoNThechemistryof[MS'j'-(M=Mo,W)anionsandtheirrelatedcompoundshavebeenextensivelyinvestigatedfortheirrelevancetobiologicalsystem,richstruc-turalchemistryandspecialreactivepropertiesaswellaspotentialapplicationinnon-linearopticalmaterials,t1~5iwhereasthatof[MSe'j'-(M=Mo,W)anionsandtheirrelatedcompoundshavereceivedattentiononlyinrecentyears.t6~7)Inl989lMhllerisolatedtwoclustercompounds,namely,cubane-like[OMoSe3Cl-(CuPPh,),j(siandlinear[WSe'(AgPPh,),).t9iAfterthat,lbersstud… 相似文献