Conformal invariance and surface critical behavior

Conformal invariance constrains the form of correlation functions near a free surface. In two dimensions, for a wide class of models, it completely determines the correlation functions at the critical point, and yields the exact values of the surface critical exponents. They are related to the bulk exponents in a non-trivial way. For the Q-state Potts model (0 Q 4) we find η_<|; = 2/(3v − 1), and for the O(N) model (−2 N 2), η_<|; = (2v − 1)/(4v − 1).     

Conformal blocks of minimal models on a Riemann surface

We give explicit integral representations for conformal blocks of minimal models on arbitrary compact Riemann surfaces.Supported by NSF under grant DMS-8505550     

非晶态WO3薄膜电致变色特性的研究

采用射频溅射三氧化钨粉末靶的技术，在不同的氧分压条件下沉积得到非晶态WO3电致变色薄膜，分析得知氧分压为1∶10的样品变色性能更好些.采用x射线衍射(XRD)，原子力显微镜(AFM)，伏安特性曲线和分光光度计分析所制备薄膜的特性.将薄膜在15mol/L的LiClO4的丙稀碳酸脂（PC）溶液进行电化学反应.发现氧分压在1∶10的情况下沉积得到的薄膜呈非晶态，薄膜有较多的孔隙，这有利于Li+的抽取，进而显示出很好的变色性能.x射线光电子能谱(XPS)成分分析表明WO3薄膜在原态中只有W和O两种原子电色反应后 关键词： 三氧化钨薄膜 非晶 射频溅射 电致变色     

Dependence of the GaAs (110) surface electronic state dispersion curves on the surface relaxation angle

The surface state dispersion curves E($\text{k}$) of the dangling bond states near the fundamental band gap, C₃ and A₅, are computed for both the established θ?27° model and the recently proposed θ?7° model of the (110) surface relaxation of GaAs, where θ is the surface bond rotation angle. The two models produce surface state dispersion curves that are similar to one another and to the data.     

X-ray rocking curves on inhomogeneous surface layers on Si single crystals

In this paper are studied the possibilities of investigating the structure of B⁺ -implanted Si single crystals by measuring X-ray rocking curves (the Bragg case). From the viewpoint of the dynamical diffraction of X-rays the structure of an implanted layer is described by a depth-profile of the statistical disorder of the layer structure and by a depth-profile of the relative change in the specific volume. These quantities take place in a modified form of the Takagi equations which are numerically computed for various values of the parameters of the layer, in order to trace their influence to the shape of the rocking curve. A great amount of free parameters and the complexity of their influence on the rocking curves make it impossible to fit the experimental and theoretical curves. On the basis of the theoretical study of the rocking curves the experimental curves measured on Si samples (dose 5×10¹⁵ cm^–2 of B⁺, energy 50–200 keV) are interpreted qualitatively.     

X-ray rocking curves on inhomogeneous surface layers on Si single crystals

Two cases of inhomogeneous surface layers are considered — diffusion layers as well as implanted layers. The parameters of the layers are investigated by means of an X-ray rocking curve analysis. In this paper the concentration profile of a diffusion layer in Si is determined from X-ray rocking curves, the rocking curves on implanted layers will be discussed in the next paper. A graph is constructed for determining approximate values of surface concentrationC ₀ and diffusion lengthL from subsidiary maxima on the X-ray rocking curve. The dependence of the shape of the rocking curves on the type of the concentration profile and on the values ofC ₀ andL was shown. The influence of crystal thickness and curvature is studied theoretically and experimentally. As an example of using this method a rocking curve of a crystal with a boron diffusion layer is measured and the parameters of the concentration profile are determined. The parameters found are proved by multiplied measurement of rocking curves after anodic oxidation and by comparing these rocking curves with theoretical ones.     

密度泛函理论研究KA油在氧化钨表面上的吸附分离

环己烷氧化生成环己酮和环己醇(产物合称KA油)是重要的工业反应,其产物环己酮可作为化学工业中重要的中间体,广泛的用于生产尼龙-6.然而,环己醇和环己酮沸点接近难以分离,因此开发有效分离KA油的材料受到科学工作者的广泛关注.本文基于密度泛函理论计算,研究KA油在干净和有机物修饰的氧化钨材料上的吸附能和吸附构型;通过差分密度电荷和态密度计算,揭示了主-客体吸附过程中的电荷转移特性;研究结果发现使用硅烷修饰后的氧化钨材料对环己醇吸附性能更好;而使用硅醚修饰后对环己酮有更强的吸附能力.该理论研究工作为实验提供了理论依据,缩短了研发分离KA油新材料的时间,节省了人力和资源等成本.     

Density functional theory study of the NO2-sensing mechanism on a WO3 (0 0 1) surface: the role of surface oxygen vacancies in the formation of NO and NO3

The trapping and detection of nitrogen oxide with tungsten trioxide has become a popular research topic in recent years. Knowledge of the complete reaction mechanism for nitrogen oxide adsorption is necessary to improve detector performance. In this work, we used density functional theory (DFT) calculations to study the adsorption characteristics and electron transfer of nitrogen dioxide on an oxygen-deficient monoclinic WO₃ (0 0 1) surface. We observed different reactions of NO₂ on slabs with different O- and WO-terminated WO₃ (0 0 1) surfaces with oxygen vacancies. Our calculations show that the bridging oxygen atom on an oxygen defect on an O-terminated WO₃ (0 0 1) surface is the active site where an NO₂ molecule is oxidised into nitrate and is adsorbed onto the surface. On a WO-terminated (0 0 1) surface, one of the oxygen atoms from the NO₂ molecule fills the oxygen vacancy, and the resulting NO fragment is adsorbed onto a W atom. Both of these adsorption models can cause an increase in the electrical resistance of WO₃. We also calculated the adsorption energies of NO₂ on slabs with different oxygen-deficient WO₃ surfaces.     

Formation of WO3 from various precursors

A comparative study of tungsten oxide formation from various precursors has been carried out using a complex of physicochemical methods. Crystallization of WO₃ has been shown to pass through metastable states in all cases. For electrodeposited oxotungstate films, the structure of tungsten oxides depends on electrodeposition conditions and adsorption properties of substrate metal with respect to hydrogen; at temperatures below 600 °C the stoichiometric composition of WO₃ is not attained.     

直流溅射法制备电致变色WO3膜

采用WO3陶瓷靶直流溅射制作了电致变色膜.介绍了制膜工艺.分析测试表明,膜有无定形结构;除有正常成分WO3外,还含有来自衬底及反应室内的微量杂质.电致变色谱响应特性和电化学特性的测量证明,膜的电色活性良好.还对实验结果作了理论分析.     

纳米WO3块体材料的电致变色效应

WO3薄膜能够通过电、光、热变色.实验发现纳米WO3块材具有明显的常规块材不具有的电致变色特性，即当样品中有电流通过时，样品从负极到正极颜色由黄色变为深蓝色.变色前后样品的显微形貌和相结构都没有明显变化.x射线光电子能谱说明变色后的样品中出现了低价的钨离子(W5+).根据实验结果，变色过程被认为是一种电子注入效应.纳米样品中的高价钨离子(W6+)因为纳米材料的表面效应而具有足够大的活性，能与电子结合生成低价的离子，从而使样品变色. 关键词： WO3块材 纳米材料 电致变色     

Conformal invariance and surface defects in the two-dimensional Ising model. Exact results

The surface critical behavior of the two-dimensional Ising model with homogeneous perturbations in the surface interactions is studied on the one-dimensional quantum version. A transfer-matrix method leads to an eigenvalue equation for the excitation energies. The spectrum at the bulk critical point is obtained using anL ^–1 expansion, whereL is the length of the Ising chain. It exhibits the towerlike structure which is characteristic of conformal models in the case of irrelevant surface perturbations (h _s /J _s 0) as well as for the relevant perturbationh _s =0 for which the surface is ordered at the bulk critical point leading to an extraordinary surface transition. The exponents are deduced from the gap amplitudes and confirmed by exact finite-size scaling calculations. Both cases are finally related through a duality transformation.     

分光光度法测定钨渣中WO3的含量

选择合适实验条件,分光光度法测定钨渣中的WO3含量,方法简便、快速、稳定,校准曲线线性关系好,可用于指导工业生产。     

WO3薄膜的电致变色特性研究

介绍了ＷＯ３电致变色薄膜的变色机理和制备工艺，对ＷＯ３薄膜的电阻率，结构，化学组玢，电化学特性和变性性能等特性进行了工艺，提出了ＷＯ３薄膜的一种新的锂化方法，这种方法对进一步研制全固态电致变色薄膜器件是十分关键的。     

Conformal invariance in semi-infinite systems: Application to critical surface scattering

We show that conformal invariance constrains the form of correction terms in the cross-section for critical surface scattering of X-rays and neutrons. We also verify inO() the conformal symmetry of the two-point order parameter correlation function of semi-infinite systems at the ordinary and special phase transition.This work was supported by Bundesministerium für Forschung und Technologie