1—苯基—4—乙基（2′—对取代苯基）环己硅烷类液晶化合物？…

运用ＡＭ１和ＰＭ３两种ＳＣＦ－ＭＯ方法,通过能量梯度全优化计算,给出４种１－苯基－４－乙基（２′－对取代苯基）环已硅烷类液晶化合物的稳定几何构型,电子结构和分子的基本性质（生成热,偶极矩等）,联系有机电子结构理论进行了细致的讨论。     

H4^＋团簇离子两种结构的能量曲线计算

此文认为在一定的条件下,Ｈ４＾＋团簇可能由一个氢核与三个氢原子相互作用而形成对称性较高的平面正三角形中心结构或正四面体结构。用ＭＡＣＱＭ方法,本文计算了这两种构型的能量曲线。结果表明：平面正三角形中心结构在中心原子核与顶角原子核间距离为２．１９ａ０时,体系出现能量极小值－１．６４８４ａ．ｕ．;正四面体结构在核间距为１．９２ａ０时,体系有一能量极小值－１．７７７７ａ．ｕ．。这说明Ｈ４＾＋的这两种结构     

一个大气氧压下Y_（0．9）Ca_（0．1）Ba_2Cu_4O_8掺Ag_2O复

在一个大气压的流动氧气氛中，通过重复烧结，合成了具有良好超导特性的Ｙ０．９Ｃａ０．１Ｂａ２ＣＵ４Ｏ８＋１０％ＷｔＡｇ２Ｏ复合块材．采用ＸＲＤ和ＳＥＭ技术对样品的结构分析表明：固相ＡＳ。Ｏ的加入对Ｙ０．９Ｃａ０．１Ｂａ２Ｃｕ４Ｏ８的相结构形成具有与熔融银添加法完全类似的加速作用；发现了存在于样品内部的Ａｇ偏聚和异常结构分布；探讨了不同掺Ａｇ２Ｏ工艺对样品结构和性能的影响．     

TATB生成焓的量子力学计算

采用Hartree-Fock方法和密度泛函 BPW91方法,对TATB分子的几何结构进行了优化,计算了其电子能量和热运动的能量.计算并讨论了TATB的生成焓.结果表明,TATB分子中的苯环离域电子结构引起TATB生成焓计算的较大的系统偏差;利用具有相似离域电子结构的苯和NO的生成焓进行修正,计算得到的TATB生成热与实验结果符合较好.?     

递归法研究Pt对Ti合金腐蚀影响

采用递归法计算了Ti及Ti合金的电子态密度、环境敏感镶嵌能、费米能级和格位能等电子结构参量.计算发现Pt在晶体中环境敏感镶嵌能和格位能高于表面,从电子层面证实Pt易在 Ti合金表面偏聚.偏聚在表面的Pt有序能为正值,故Pt以有序相（Pt与Ti的化合物）形式分布在合金表面.晶体表面Pt 与Ti的化合物电极电位较低,它与Ti形成微电池.在腐蚀介质的作用下,Pt与Ti的化合物分解,Pt沉淀到晶体表面造成Pt在合金表面形成凹凸不平的Pt电催化层.Pt电催化层加强Ti钝化作用,从而提高了Ti合金的抗腐蚀能力. 关键词： 电子结构 Ti合金表面 钝化     

非晶态Fe0.5Al0.5PO4表面上激光促进甲烷直接氧化合成甲醇的研究

用溶胶－凝胶法合成了非晶态Ｆｅ０．５Ａｌ０．５ＰＯ４。用ＸＲＤ和ＴＰＲ表征了其结构和晶格氧的活性;用ＩＲ和ＴＰＤ表征了ＣＨ４在其表面上的吸附行为;用ＬＳＳＲ方法考察了ＣＨ４直接氧化合成ＣＨ３ＯＨ的反应规律。结果表明,Ｆｅ０．５Ａｌ０．５ＰＯ４具有非晶态的结构,ＦｅＰＯ４和ＡｌＰＯ４的微区被均匀地相互隔离,导致固体本身不具有长程有序性。非晶态的Ｆｅ０．５Ａｌ０．５ＰＯ４与晶态的Ｆｅ０．５Ａｌ０．５Ｐ     

用类氧原子波函数计算H7^—团簇正八体中心结构的能量曲线

选用类氧原子波函数,在单中心球模型近似下,利用变分法计算了Ｈ７＾－团簇正八面体中心结构的能量曲线。结果表明,当中心Ｈ原子核能顶角Ｈ原子核之间的距离Ｒ＝１．５８ａ０时,体系能量有一极小值－４．０８９９４５３ｈ．ａ．ｕ．。这表明Ｈ７的正八面体中心结构是可能稳定存在的。计算结果与用ＭＡＣＱＭ法计算的结果基本相符,表明提出的物理模型及其计算方法是合理的。     

丝光沸石的Monte Carla研究：Ⅱ.脱铝丝光沸石的骨架硅,铝分布

以马尔可夫链近似模拟线光沸石脱铝过程，用ＭｏｎｔｅＣａｒｌｏ方法计算脱铝丝光沸石中骨架Ｓｉ－Ａｌ近邻分布｛Ｓｉ（ｎ－Ａｌ）；ｎ＝０－４｝和Ａｌ－Ａｌ次部分布｛Ａｌ（ｍ－Ａｌ）；ｍ＝０－３｝随铝浓度的演化。为使Ｓｉ－Ａｌ近邻分布与对脱铝丝光沸石样品的＾２＾９ＳｉＭＡＳＮＭＲ观测相符，而得到丝光沸石弱酸铝易于解脱的结论，这个结构与八面沸石弱酸铝易于解脱相反。根据计算丝光沸石脱铝的开始阶段，强酸中心...     

5‘—硝基—水杨基荧光酮—溴化十六烷基三甲胺荧光猝灭法测定？…

本文基于Ｚｒ（Ⅳ）５‘－硝基－水杨基荧光酮－溴化十六烷基三甲铵（ＣＴＭＡＢ）体系的荧光猝灭效应,提出一种测定微量锆的新荧光分析方法。在０．８－１．２--ｍｏｌ／Ｌ的Ｈ２ＳＯ４介质中,ＣＴＭＡＢ存在下,锆与５’－Ｎ－ＳＡＦ生成组成比为１：４的橙红色络合物。     

光调制红外热像仪的设计与有限元模拟

新型热像仪是一种基于微机械技术的光调制热成像系统,它采用光调制原理来实现像转换和像增强,春核心是一个采用与互补型金属氧化物半导体工艺相溶的微机械技术制作的光调制热成像器件。该系统具有一系列潜在的优点：灵敏度和分辨率高、体积和能耗小、响应时间短并可在室温下工作。叙述了器件的设计和建模,通过一种简化的悬臂梁理论计算了其灵敏度、最小可探测能量及响应时间等参数,并对双材料梁的设计进行了优化。采用ＡＮＳＹＳ５．４程序对设计的器件进行了有限元模拟,得到的灵敏度和响应时间分别为０．０３ｍ／Ｗ和６ｍｓ。     

氧原子在X@Al12 (X=C，Si，P+ )团簇吸附性质的研究

利用密度泛函理论了对X@Al12 (X=C, Si, P+)团簇吸附氧原子特性进行了研究,分别分析了氧原子在三个吸附位置(顶位置、桥位置和空位置)的氧原子吸附能,HOMO-LOMO能隙和电荷转移等性质。结果表明氧原子更倾向于吸附在空位位置。C@Al12和Si@Al12, P+@Al12 在对氧的吸附性质上比较接近。氧在X@Al12(X= C, Si, P+)的吸附性质与Al13−有显著不同。在Al13−O中O是倾向于以桥位形式吸附在Al13−上的。X@Al12(X=C, Si, P+)和Al13−的电子结构有着明显的差异,这导致了O在这些团簇表面不同的吸附形式,表明掺杂可以有效的改变团簇的性质。     

氧原子在X@Al12 (X=C，Si，P+ )团簇吸附性质的研究

利用密度泛函理论了对X@Al12 (X=C, Si, P+)团簇吸附氧原子特性进行了研究,分别分析了氧原子在三个吸附位置(顶位置、桥位置和空位置)的氧原子吸附能,HOMO-LOMO能隙和电荷转移等性质。结果表明氧原子更倾向于吸附在空位位置。C@Al12和Si@Al12, P+@Al12 在对氧的吸附性质上比较接近。氧在X@Al12(X= C, Si, P+)的吸附性质与Al13−有显著不同。在Al13−O中O是倾向于以桥位形式吸附在Al13−上的。X@Al12(X=C, Si, P+)和Al13−的电子结构有着明显的差异,这导致了O在这些团簇表面不同的吸附形式,表明掺杂可以有效的改变团簇的性质。     

The interplay between the lattice and magnetism in La(Fe_11.4Al_1.6)C_0.02 studied by powder neutron diffraction

The crystallographic structure and magnetic properties of La(Fe 11.4 Al 1.6 )C 0.02 are studied by magnetic measure- ment and powder neutron diffraction with temperature and applied magnetic field. Rietveld refinement shows that La(Fe 11.4 Al 1.6 )C 0.02 crystallizes into the cubic NaZn 13 -type with two different Fe sites: Fe I (8b) and Fe II (96i), and that Al atoms preferentially occupy the Fe II site. A ferromagnetic state can be induced at a medial temperature of 39 K–139 K by an external magnetic field of 0.7 T, and a large lattice is correspondingly found at 100 K and 0.7 T. In all other conditions, La(Fe 11.4 Al 1.6 )C 0.02 has no net magnetization in the paramagnetic (T > T N = 182 K) or antifer- romagnetic states, and thus keeps its small lattice. Analysis of the Fe–Fe bond length indicates that the ferromagnetic state prefers longer Fe–Fe distances.     

Fe-Si-Al合金结构的研究

本文叙述了利用电子显微镜对含10％Si和5％Al的Fe-Si-Al高导磁合金薄膜进行的结构研究。发现了基体为有序面心立方Fe₃(Al,Si)结构,其晶格参数为5.70±0.03?,该值在Fe₃Si和Fe₃Al晶格参数之间,说明部分Si原子为Al原子所置换。并获得三套基体和析出相合成的电子衍射图,相应确定了基体和析出相的取向关系:(001)_基‖(110)_相;[100]_基‖[00I]_相;[010]_基‖[I10]_相。对析出相的萃取碳复型,在电子显微镜中进行选区衍射,获得了立方Fe₃(Al,Si)C_x相的结构。提出:Fe原子占据面心;Al或Si原子占据顶角;C原子占据体心的看法。 关键词：     

Atomic and electronic structures of p-type dopants in 4H-SiC

Using hybrid density functional calculation,we study the atomic and electronic structures of p-type dopants,B,Al and Ga,in 4 H-SiC.For B,depending on the growth condition,it can occupy both Si and C sites.In contrast,Al and Ga on the C sites exhibit too high formation energy to exist in a significant amount.In 4 H-SiC,there exist two types of Si sites in wurtzite-like and zincblende-like local coordination,respectively.Our calculations suggest that the dopant atoms have negligible preference occupying the two sites.In neutral charge state,all the dopants exhibit significant distortions from the structure in the negatively charged state.For most cases,our calculations yield three distorted structures,in which the most stable one has the dopant atom displaced along its bond with one of the surrounding equatorial Si or C atoms,lowering the C_(3 v) symmetry to Cs symmetry(i.e.,a mirror symmetry only).Among the three dopant elements,Al on Si sites exhibits overall the lowest formation energy and the shallowest acceptor level.Nevertheless,it is not a hydrogenic dopant with the acceptor level 0.12 eV above the valence band maximum based on calculation using a 400-atom supercell.Its corresponding defect state exhibits apparent localization along the [0001] direction,but it is relatively delocalized in the(0001) plane.     

Features of atomic and electronic structure of oxides on porous silicon surface according to XANES data

Based on synchrotron research of the fine structure main parameters of SiL _{2, 3} X-ray absorption edges (X-ray absorption near edge structure (XANES)) in porous silicon on boron-doped Si(100) wafers, the thickness of the surface oxide layer and the degree of distortions of the silicon-oxygen tetrahedron in this layer were estimated. The thickness of the oxide layer formed on the amorphous layer coating nanocrystals of porous silicon exceeds the thickness of the native oxide on the surface of Si(100) : P and Si(100) : B single-crystal (100) silicon wafers by several times. Distortion of the silicon-oxygen tetrahedron, i.e., the basic unit of silicon oxide, is accompanied by Si-O bond stretching and an increase in the angle between Si-O-Si bonds.     

Effect of hydrogenation on P/Si(0 0 1)-(1 × 2)

Ab initio calculations, based on pseudopotentials and density functional theory, have been performed to investigate the effect of hydrogenation on the atomic geometries and energetics of substitutional phosphorus (P) on the generic Si(0 0 1)-(1 × 2) surface. For the 0.5 ML coverage of P, we have considered three different substitutional sites: (i) the mixed Si-P dimer structure (i.e., the P-nondiffused case), (ii) P-interdiffused to the second layer Si (i.e., intermixed P-Si bond structure) and (iii) P-interdiffused to the third layer Si. We have found that the mixed Si-P dimer structure is 0.79 eV/dimer energetically more favorable than the P-interdiffused case. However, for the hydrogenation of above cases, we have found that the situation is reversed and the interdiffused case is 0.3 eV/dimer energetically more favorable than the P-nondiffused case. Reductions in the number of P-Si is identified as a contributing factor which determines energetically the stable structures during P on Si(0 0 1).     

Formation of noble metal particles by ultrasonic irradiation

It was found that sonochemically prepared metal particles such as Ag, Pd, Au, Pt and Rh are of nanometer size with a fairly narrow distribution (e.g., about 5 nm for Pd particles obtained from a 1.0 mM Pd(II) in polyethylene glycol monostearate solution). We have suggested three different reduction pathways under sonication: (i) reduction by H atoms, (ii) reduction by secondary reducing radicals formed by hydrogen abstraction from organic additives with OH radicals and H atoms, (iii) reduction by radicals formed from pyrolysis of the additives at the interfacial region between cavitation bubbles and the bulk solution. The reduction of Ag(I) and Pt(II) mainly proceeds through reaction pathway (ii). In the cases of Pd(II) and Au(III), the reductions mainly proceed through reaction pathway (iii). The reduction of Rh(III) was not achieved under the same conditions; however, by the addition of sodium formate, reduction occurred and the preparation of Rh particles succeeded.     

Early stages of vanadium deposition on Si(1 1 1)-7 × 7

We investigate the low-coverage regime of vanadium deposition on the Si(1 1 1)-7 × 7 surface using a combination of scanning tunnelling microscopy (STM) and density-functional theory (DFT) adsorption energy calculations. We theoretically identify the most stable structures in this system: (i) substitutional vanadium atoms at silicon adatom positions; (ii) interstitial vanadium atoms between silicon adatoms and rest atoms; and (iii) interstitial vanadium - silicon adatom vacancy complexes. STM images reveal two simple vanadium-related features near the Si adatom positions: bright spots at both polarities (BB) and dark spots for empty and bright spots for filled states (DB). We relate the BB spots to the interstitial structures and the DB spots to substitutional structures.     

Si在TiAl3中取代行为的第一性原理研究

采用基于密度泛函理论的第一性原理方法,研究了Si原子在TiAl3中的格点取代行为.通过对不同原子被置换后的c/a值、形成能以及电子态密度的计算和比较,发现Si原子倾向于取代TiAl3中的Al原子,其取代行为主要由系统的电子结构决定,计算结果与实验相符.为了进一步研究Si原子的取代行为,对Si原子占据的格点以松散或紧凑分布下体系的总能、形成能以及电子态密度进行了计算,结果表明Si原子倾向于取代TiAl3中松散分布的Al(2)原子.对c/a值的计算表明,随Al(2)格点Si原子浓度的增加,c/a值逐渐增大;而当Si取代Al(1)格点时,c/a值随Si原子浓度的增加而减小.研究表明,Si在TiAl3中的极限固溶度介于12.5at%-18.75at%之间.