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X光衍射中积分强度的近似公式 总被引:1,自引:0,他引:1
用X射线衍射仪做定量分析衍射实验时会因盖革记数器的死时间而出现漏计现象.为了简便地测定死时间,本文提出了单层膜两次照射技术,导出了校正积分强度的近似公式,并与逐次校正法作了对比分析。 相似文献
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Conclusions We have shown that in the absence of texture and extinction effects two kinds of reduction in the diffraction line intensity are observed after plastic deformation: a) a reduction obeying the same law as that due to a temperature rise and b) a reduction similar to that produced by the appearance of a new phase. The former is attributable to nonunifrom elastic strains produced by stress fields associated with dislocations. The latter is attributable to the fact that certain crystal regions near the dislocation lines are so heavily distorted that they make no contribution to X-ray diffraction. 相似文献
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X射线衍射的发现 总被引:1,自引:0,他引:1
简单介绍了埃瓦尔德(Ewald P P)、劳厄(von Laue M)和布拉格父子(Bragg W H及Bragg W L)在1912年发现X射线衍射方面的贡献.1911年埃瓦尔德在索末菲的指导下在慕尼黑大学从事博士论文研究,劳厄在与他的讨论中了解到晶格的平移周期与X射线的波长属于同一量级,因此想到在二维光栅的两个衍射方程组中再加一个类似的方程,就可以描述X射线在三维晶体中的衍射.在此假设的指导下,Friedrieh W和Knipping P在1912年4月开始用CuSO4后来用闪锌矿(立方ZnS)进行实验,很快就得到X射线衍射的证据.这不但证明了X射线的波动性,还确定了晶体的三维周期性.老布拉格在1912年夏得知这个消息,与他儿子小布拉格一道尝试用X射线的粒子性解释它,并由小布拉格在剑桥大学重复这个实验.根据衍射斑点的椭圆形状和从Pope与Below那里学到的晶格理论(由此得知ZnS具有面心立方晶格),小布拉格将X射线在晶体中的衍射看作是X射线从一些晶格平面的反射,从而推导出著名的布拉格方程.布拉格父子开拓了X射线晶体结构分析这门新兴学科,从简单的无机化合物和矿物,逐渐发展到有机化合物和生物大分子.劳厄和布拉格父子分别强调慕尼黑和剑桥的优良科学环境对发现X射线衍射的重要性.鉴于埃瓦尔德在发现X射线衍射的作用及他后来在倒易格子及动力学衍射理论方面的贡献,不少晶体学家认为他也应获得诺贝尔物理奖. 相似文献
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We present here the detailed results of X-ray diffraction from single quasicrystals of Al6CuLi3. X-ray precession photographs taken down the two-, three- and five-fold axes along with rotation and zero-level Weissenberg
photographs are shown. Preliminary analysis of the diffraction data rules out the twin hypothesis. 相似文献
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In order to obtain more structural details from X-ray diffraction (XRD) patterns of metallic multilayers we developed a simulation program for XRD patterns of Al/Nb multilayers. We followed the theory of an imperfect one-dimensional superlattice described by Z. Mitura and P. Mikolajczak. Computer simulated patterns are compared with experimentally obtained XRD spectra. 相似文献
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I. L. Shulpina E. V. Suvorov 《Bulletin of the Russian Academy of Sciences: Physics》2010,74(11):1488-1496
The possibilities of high-resolution X-ray section topography using the geometry of the interference bands to reveal features
of the elastic fields of crystalline lattice defects are considered. The mechanisms of the diffraction of the X-ray wavefield
on elastic lattice distortions are demonstrated using the example of dislocations. Microdefects in silicon are another most
interesting subject. Section topography is in this case virtually the only method for revealing very weak deformations due
to microdefects. 相似文献
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R. Brajpuriya S. Tripathi S.M. Chaudhari D.M. Phase T. Shripathi U. Pietsch 《Applied Surface Science》2007,253(21):8584-8587
In situ temperature dependent energy-dispersive structural and magnetic study of electron beam evaporated Fe/Al multilayer sample (MLS) has been investigated. The structural studies show the formation of an intermixed FeAl transition layer of a few nanometers thick at the interface during deposition, which on annealing at 300 °C transforms to B2FeAl intermetallic phase. Magnetization decreases with increase in temperature and drops to minimum above 300 °C due to increase in anti-ferromagnetic interlayer coupling and formation of nonmagnetic FeAl phase at the interface. The Curie temperature (Tc) is found to be 288 °C and is much less than that of bulk bcc Fe. 相似文献
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J. Kuběna 《Czechoslovak Journal of Physics》1968,18(6):777-783
The importance of respecting the coherent properties of X-rays in the physical interpretation of the profiles of the X-ray diffraction patterns is pointed out. Drawing the analogy between Young's experiment and two-atom X-ray scattering, the author applies the elementary theory of coherence, developed for light optics, to X-ray diffraction by a linear atomic lattice. As his considerations concerning the effect of coherence on diffraction by such a lattice are impossible to verify experimentallly, he tests their correctness by spectrographical measurements of the width of an optical grating diffraction line under different coherence and experimental conditions.
The paper is dedicated to the memory of Dr. A. Vaíek, Professor of the J. E. Purkyn University in Brno, who died on November 16, 1966. 相似文献
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H. Palancher S. Bos J. F. Bérar I. Margiolaki J. L. Hodeau 《The European physical journal. Special topics》2012,208(1):275-289
X-ray resonant diffraction can be applied in structural chemistry studies on powder samples. It enables an important limitation of powder diffraction to be overcome. This limitation is related to the low ability of powder diffraction to differentiate elements with close atomic numbers when they occupy the same or close crystallographic sites (mixed occupancy case) and also to discriminate cations with different valence states in different sites. However the resonant effect usually has a second order influence on the measured intensity. As a consequence, the efficiency of this method directly implies the need for excellent quality data collection and has generally been better assessed on elements present in single phase powder samples. In recent years, instrumental developments have been made in synchrotron radiation facilities which allow easier use of resonant powder diffraction for site-specific contrast and valence i.e. oxidation state analyses. Moreover, resonant contrast diffraction tools also have been proposed for better visualization of the anomalous effect both in direct and reciprocal space by using differences between electron density maps or diffraction patterns. Finally the potentialities of this technique for de novo structure solution on macromolecular systems are mentioned. 相似文献
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用X射线衍射仪做定量分析衍射实验,会出现因盖革计数器存在分辨时间而漏计的现象.为了简便地测定分辨时间,本文利用单层膜二次照射技术,导出了用来校正积分强度的近似公式,并与逐点校正法作了对比分析,二者符合很好. 相似文献
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Wan-Li Shang 《中国物理 B》2021,30(11):116101-116101
Plasma density and temperature can be diagnosed by x-ray line emission measurement with crystal, and bent crystals such as von Hamos and Hall structures are proposed to improve the diffraction brightness. In this study, a straightforward solution for the focusing schemes of flat and bent crystals is provided. Simulations with XOP code are performed to validate the analytical model, and good agreements are achieved. The von Hamos or multi-cone crystal can lead to several hundred times intensity enhancements for a 200μm plasma source. This model benefits the applications of the focusing bent crystals. 相似文献
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V. Kleinwächter 《Czechoslovak Journal of Physics》1960,10(3):191-194
Denatured ferritin, in contrast to other denatured corpuscular proteins, gives several diffractions, even in the regiond>15 Å. These diffractions correspond to the mutual arrangement of the micelles and proteinic component of ferritin. Diffractions in the regiond<15 Å correspond both to the internal structure of the denatured proteinic component — apoferritin — and to the internal structure of ferric micelles of ferritin. Regions containing only the denatured proteinic component with polypeptide chains in-configuration, occur in the structure of denatured ferritin in addition to the crystallites or crystalline regions with regular arrangement of micelles and the proteinic component.
, , d>15 Å. . d<15 Å — , — . , gb-.相似文献
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Wilkins SB Hatton PD Roper MD Prabhakaran D Boothroyd AT 《Physical review letters》2003,90(18):187201
We have conducted the first soft x-ray diffraction experiments from a bulk single crystal, studying the bilayer manganite La2-2xSr1+2xMn2O7 with x=0.475 in which we were able to access the (002) Bragg reflection using soft x rays. The Bragg reflection displays a strong resonant enhancement at the L(III) and L(II) manganese absorption edges. We demonstrate that the resonant enhancement of the magnetic diffraction of the (001) is extremely large, indeed so large that it exceeds that of the nonresonant Bragg diffraction. Resonant soft x-ray scattering of 3d transition metal oxides is the only technique for the atomic selective measurement of spin, charge, and orbital correlations in materials, such as high temperature superconductors, colossal magnetoresistance manganites, and charge stripe nickelates. 相似文献
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Andrzej Katrusiak 《高压研究》2013,33(5):265-275
Abstract Dimedone (i.e. 5.5-dimethyl-I,3-cyclohexanedione) crystals, C8HI12O2, have been studied at high pressures by X-ray diffraction using a Merrill-Bassett diamond-anvil cell. The unit-cell dimensions have been measured to 1.20(5) GPa and the structure has been determined at 0.95(5) GPa. The crystal compressibility is strongly anisotropic and non-linear, relatively strong compressibility of the crystals is observed along the helices of the hydrogen-bonded molecules. Small anomalous changes of the unit-cell dimensions are observed between 0.1 and 50 MPa. The main structural changes are compression of intermolecular contacts, but also an alongation of the O=C bond—accompanied with the compression of the hydrogen bond involving the carbonyl oxygen atom—has been observed. This elongation is consistent with similar effects reported on compression of the hydrogen bonds in 1,3-cyclohexanedione and 2-methyl-1,3-cyclopentanedione. Crystal data for the dimedone structure at 0.95 GPa: monoclinic, P21/c, a=9.909(6), b= 6.505(3), c=12.313(6) Å, β=14.51°, V=722.1(5) Å, Z=4, R=0.139 for 336 independent reflections. 相似文献