Electron diffraction interpretation of patterns

K. Andrews, D. Dyson and S. Keown, Interpretation of Electron Diffraction Patterns , Plenum Publishing, New York, 1971. Has many examples for selected area electron diffraction. 

A thermal analysis (14) of BeBr2 up to temperatures near the melting point showed no polymorphic modifications. Also, the interpretation of electron-diffraction patterns for freshly sublimed BeBr Indicated that it is isostructural with the o form... 

The most direct approach to the geometric structures of molecules and also of clusters in the gas phase are diffraction methods, in particular the diffraction of an electron beam. Since an adequate cluster flux for such electron diffraction experiments has been so far only possible, if the full source output beam was sampled, the uncertainties in cluster size (no mass-selection) and internal energy prevent an unambiguous interpretation of electron diffraction patterns [138-145]. In a new development, a technique has been recently reported that relies upon an rf-Paul trap [146] to take advantage of the current... 

K. W. Andrews, D. J. Dyson, S. R. Keown Interpretation of Electron Diffraction Patterns, Hilger Walls, London l%7. 

At present therefore, the details of most atomic structures must be discovered indirectly. The experimental material for the purpose is the X-ray diffraction pattern. Electron diffraction patterns and neutron diffraction patterns are similar, and have been used for the same purpose but the great majority of investigations of crystal structure are based on X-ray diffraction patterns. The interpretation of these diffraction patterns falls into two stages—first, the determination of the shape and dimensions of the unit cell (see Chapter II), and second, the discovery of the positions of the atoms in the unit cell. 

Electron diffraction studies by Roche et al.96) of annealed fibres have revealed a fibre repeat of 1,24 nm which remains constant even when the processing conditions are varied. This value is in good agreement with the length of 1.247 nm of t-bisthiazole as measured by the C(8) to C(5 )separation by Wellmann et al. 97). This implies that the PBT chain has the fully extended conformation, since the fibre repeat consists of only one repeat unit. The electron diffraction patterns have also been interpreted in terms of monoclinic and triclinic unit cells but a more definite assignment may be possible with more highly ordered fibres. 

X-ray or electron diffraction analyses are commonly employed to determine mineral species. In the case of biophosphates, these techniques are limited because the material is a complex mixture of organics and inorganics and furthermore the crystallites are small. Thus, resolution of X-ray diffraction pattern of bone and dentin material is rather poor. Electron diffraction pattern is generally better, but there is always the possibility of secondary alteration of the specimen during exposure. Other methods — such as infrared analysis — have their limitations too. In short, there are some analytical problems which may in part account for the conflicting interpretations offered in the literature. 

Consequently, we can interpret the superlattice maxima exhibited in the electron diffraction pattern of Fig. 10b as originating from a framework with essentially the ZSM-5 structure (successive planes along are related by j ) but with ... 

The electron-diffraction pattern of the vapor can be satisfactorily interpreted, like the vibrational properties, on the basis of a molecule H2Ga(p.-Cl)2GaH2 with D2h symmetry, as illustrated in Fig. 3. Here... 

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