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Bernal Chart
A Bernal chart (bər′nal ′chärt) in crystallography, is a chart used for indexing X-ray diffraction photographs from single crystals. From such a chart may be read the axial and radial cylindrical coordinates of that point in reciprocal space which corresponds to any particular X-ray reflection. When a single crystal is examined in an X-ray diffractometer such that the diffraction intensity is measured cylindrically around the crystal, it is convenient to use cylindrical coordinates to define the reciprocal lattice vectors and their terminal points. Different order reflections will be coaxial with the axis of rotation. These reflections are recorded as spots which lie on parallel lines known as layer lines. A reciprocal lattice vector can be represented by two mutually perpendicular vectors \zeta (along the rotation axis) and \xi in the horizontal plane (the plane perpendicular to the rotation axis) containing the X-ray beam. The third parameter specifying the reciprocal lattic ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Crystallography
Crystallography is the experimental science of determining the arrangement of atoms in crystalline solids. Crystallography is a fundamental subject in the fields of materials science and solid-state physics (condensed matter physics). The word "crystallography" is derived from the Greek word κρύσταλλος (''krystallos'') "clear ice, rock-crystal", with its meaning extending to all solids with some degree of transparency, and γράφειν (''graphein'') "to write". In July 2012, the United Nations recognised the importance of the science of crystallography by proclaiming that 2014 would be the International Year of Crystallography. denote a direction vector (in real space). * Coordinates in ''angle brackets'' or ''chevrons'' such as <100> denote a ''family'' of directions which are related by symmetry operations. In the cubic crystal system for example, would mean 00 10 01/nowiki> or the negative of any of those directions. * Miller indices in ''parentheses'' ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Chart
A chart (sometimes known as a graph) is a graphical representation for data visualization, in which "the data is represented by symbols, such as bars in a bar chart, lines in a line chart, or slices in a pie chart". A chart can represent tabular numeric data, functions or some kinds of quality structure and provides different info. The term "chart" as a graphical representation of data has multiple meanings: * A data chart is a type of diagram or graph, that organizes and represents a set of numerical or qualitative data. * Maps that are adorned with extra information (map surround) for a specific purpose are often known as charts, such as a nautical chart or aeronautical chart, typically spread over several map sheets. * Other domain-specific constructs are sometimes called charts, such as the chord chart in music notation or a record chart for album popularity. Charts are often used to ease understanding of large quantities of data and the relationships between parts of t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Diffractometer
A diffractometer is a measuring instrument for analyzing the structure of a material from the scattering pattern produced when a beam of radiation or particles (such as X-rays or neutrons) interacts with it. Principle Because it is relatively easy to use electrons or neutrons having wavelengths smaller than a nanometer, electrons and neutrons may be used to study crystal structure in a manner very similar to X-ray diffraction. Electrons do not penetrate as deeply into matter as X-rays, hence electron diffraction reveals structure near the surface; neutrons do penetrate easily and have an advantage that they possess an intrinsic magnetic moment that causes them to interact differently with atoms having different alignments of their magnetic moments. A typical diffractometer consists of a source of radiation, a monochromator to choose the wavelength, slits to adjust the shape of the beam, a sample and a detector. In a more complicated apparatus, a goniometer can also be used for fi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Greninger Chart
In crystallography, a Greninger chartIt is named after Alden Buchanan Greninger (17 September 1907, Glendale, Oregon20 April 1998). is a chart that allows angular relations between zones and planes in a crystal to be directly read from an x-ray diffraction photograph. The Greninger chart is a simple trigonometric tool to determine ''g'' and ''d'' for a fixed sample-to-film distance. (If one uses a 2-d detector the problem of determining ''g'' and ''d'' could be solved mathematically using the equations which generate the Greninger chart) A new chart must be generated for different sample to detector distances. (2''s'' is 2''q'' for the diffraction peak and tan ''m'' is ''x''/''y'' for the Cartesian coordinates of the diffraction peak.) The Greninger chart gives directly the two angles needed to plot poles on the Wulff net. It is critical to keep track of the relative arrangement of the sample to the film, if photographic film is used then this is achieved by cutting the corne ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
John Desmond Bernal
John Desmond Bernal (; 10 May 1901 – 15 September 1971) was an Irish scientist who pioneered the use of X-ray crystallography in molecular biology. He published extensively on the history of science. In addition, Bernal wrote popular books on science and society. He was a communist activist and a member of the Communist Party of Great Britain (CPGB). Education and early life His family was Irish, of mixed Spanish, Portuguese and Italian Sephardic origin on his father's side (his grandfather Jacob Genese, properly Ginesi, had adopted the family name Bernal of his paternal grandmother around 1837). His father Samuel Bernal had been raised as a Catholic in Limerick and after graduating from Albert Agricultural College spent 14 years in Australia before returning to Tipperary to buy a farm, ''Brookwatson'', near Nenagh where Bernal was brought up. His American mother, née Elizabeth Miller, whose mother was from Antrim, was a graduate of Stanford University and a journalist a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
