![]() ![]() Some ideas about crystal structure were generally accepted, while others were poorly understood and hotly debated. They hypothesized about atomic arrangements and the nature of crystal structures, but they lacked direct evidence. By the late nineteenth century, mineralogists knew that crystals had ordered and repetitive crystal structures. Scientists studied minerals for hundreds of years before the discovery of X-rays. Other important analytical techniques include X-ray fluorescence, atomic absorption, inductively coupled plasma mass spectrometry, ion microprobe, Mössbauer spectroscopy, visible and infrared spectroscopy, and Raman spectroscopy.ġ2.1 X-ray Diffraction 12.1.1 The Discovery of X-rays and Diffraction.Electron microprobe data yield mineral compositions based on X-ray intensities.Scanning electron microscopes allow high-magnification imaging of mineral crystals and of thin sections.Single crystal diffraction data allow crystallographers to figure out where atoms are in a unit cell.Compositional variations cause slight variations in X-ray patterns.We use a powdered sample for routine mineral identification.Directions of diffraction tell us the spacings between planes of atoms in a crystal intensities of diffraction tell us the number of atoms on those planes.When X-rays interact with atoms, the rays are scattered in all directions coherent scattering by multiple atoms produces X-ray diffraction.X-rays may have many different wavelengths but for diffraction studies we isolate one.X-radiation, discovered in 1895, was the key to understanding atomic arrangements in crystals.The critical importance of the phases of the diffracted waves in structural analysis is demonstrated, and then, the experimental determination of phases in protein X-ray crystallography is briefly introduced.12.1 A powder X-ray diffractometer 12 X-ray Diffraction and Mineral Analysis By applying this theory to a system composed of two or more electrons, the interference between the diffracted waves is described as the Fourier transform of the electron density in the system. The theory of dipole radiation is applied to electrons bound in atoms, and then the scattering cross section for Thomson scattering is derived. First, fundamental equations are derived to describe electromagnetic waves emitted from accelerated electrons by solving Maxwell’s equation. In this chapter, the theoretical background of X-ray diffraction is introduced starting from Maxwell’s equation in the system of non-relativistic classical electromagnetism. The critical importance of the phases of the diffracted waves in structural analysis is demonstrated, and then, the experimental determination of phases in protein X-ray crystallography is briefly introduced.ĪB - X-ray diffraction is the basis for understanding X-ray diffraction imaging (XDI). ![]() ![]() N2 - X-ray diffraction is the basis for understanding X-ray diffraction imaging (XDI). © 2018, Springer Japan KK, part of Springer Nature.
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