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Bragg position

Note that x translates into the derivative dB/dn of the lattice gas, and hence measures the increase in coverage as the adsorbate gas pressure increases, assuming there is equilibrium between the layer and surrounding gas. The quantity k Tx is proportional to the peak intensity of the diffuse scattering at the Bragg position corresponding to the overlayer ordering described by the order parameter... [Pg.105]

From LEED measurements of H monolayers adsorbed on Fe(110) Imbihl et al. proposed a phase diagram as shown in Fig. IS. In addition to lattice gas and lattice fluid phases, two commensurate ordered phases were identifled, denoted as (2 x 1) and (3 x 1) in the figure (cf. Fig. 16). The shaded regions are interpreted as incommensurate phases or as phases composed of antiphase domains their signature is that the LEED spot does not occur at the Bragg position but rather the peak is splitted and satellites appear (Fig. 17). [Pg.122]

Figure 4.6 A high resolution experiment. In (a) the crystal is not yet aligned to the Bragg position and no diffracted beam occurs. In (b) the incident beam s been rotated so that the Ewald sphere falls on the 004 relp, and a diffracted beam ensues. The Ewald sphere is to scale for CuK and the reciprocal lattice is to scale for silicon... Figure 4.6 A high resolution experiment. In (a) the crystal is not yet aligned to the Bragg position and no diffracted beam occurs. In (b) the incident beam s been rotated so that the Ewald sphere falls on the 004 relp, and a diffracted beam ensues. The Ewald sphere is to scale for CuK and the reciprocal lattice is to scale for silicon...
Many things do, or may, go into making up each yj. At a mini -mium there is a background plus contributions from the "tails" of all nearby reflections (Fig. 2). Let G(0 -6H) represent the Htil individual reflection profile centered at the Bragg position, 0. Let y-jnH represent a net intensity, above background, contributed by the Bragg reflection and let yib be the background level at this i- fe position. Then... [Pg.70]

Figure 12. Dark-field micrograph of the cross section of an Ag,S-stained Type 2 (see text) PA 66 fiber. Notice black deposits of silver sulfide in the periphery and white dots in the whole section, corresponding to crystallites in Bragg position. Figure 12. Dark-field micrograph of the cross section of an Ag,S-stained Type 2 (see text) PA 66 fiber. Notice black deposits of silver sulfide in the periphery and white dots in the whole section, corresponding to crystallites in Bragg position.
Bragg positions k+l=2n+ at room-temperature. In synthetic titanite such diffuse reflections occur in the P phase only. The diffuse reflections in natural samples have extended 2-dimensional scattering normal to the crystallographic a-axis and show strong variation with temperature (Malcherek et al. [Pg.276]

Faulting also produces a shift from the Bragg position given by ... [Pg.408]

Consider a polycrystalline sample irradiated by a monochromatic X-ray beam. This sample contains a very high number of grains and if these crystals are randomly oriented, then for each farttily of planes (hkl) a large nurrrber of grains are in the Bragg position and therefore diffract. As we have seen, the diffracted beams are at an angle equal to 20 with the direction of the incident beam. [Pg.34]

Therefore, the locus of all the bearrrs diffracted by the entire set of crystals in the Bragg position is a cone with a half opening angle 20. If we take into account diffraction by several farrrilies of planes, the resrrlt is a series of diffraction cones sharing the same apex (see Figure 1.17). [Pg.34]

Let M be the number of elementaiy ciystals contained in the sample and let 8V be the average elementary volume of each of these crystals. We are going to calculate the expression of the intensity diffracted by m crystals in the Bragg position for a given family of planes (hkl). [Pg.35]

Figure 1.18. Calculation of the number of grains in the Bragg position for a given family ofplanes... Figure 1.18. Calculation of the number of grains in the Bragg position for a given family ofplanes...
In a crystal, there are several families of planes with different orientations but with the same interplanar distance and the same stmcture factor modulus. In the case of a polycrystalline sample, these different families will diffract simultaneously and, will therefore contribute to the overall intensity of the peak in question, rihki denotes the number of equivalent families of planes for a given triplet (hkl) and n is the multiplicity factor of the diffraction peak being studied. If we wish to calculate the number of famihes of planes (hkl) in the Bragg position, we will have to multipty the resulting value by uhh. [Pg.35]

The intensity of a peak (hkl) is equal to the number of crystals in the Bragg position multiplied by the intensity diffracted by an elementary crystal. If the total volume of the sample is equal to dV, then dV = M8V and the total volume of the crystals in the Bragg position is equal to the number of grains multiplied by the volume of each grain. Hence the volume is expressed as follows ... [Pg.36]

In both cases, the quantity of material used is veiy small, since the analysis is transmission-based, making it important to limit the absorption by the sample. In order to prevent effects caused by too small a number of grains, the stand for the sample holder can rotate, so that each grain can be, in turn, placed in the Bragg position for different famihes of planes. [Pg.75]

A few years after the first experiments led by Debye, Scherrer and Hull, Seemaim [SEE 19] andBohhn [BOH 20] thought of an X-ray diffraction apparatus for polycrystalline samples that would detect where they converge the beams diffracted by the crystals in the Bragg position. The corresponding configuration is shown in Figure 2.38. [Pg.87]

This sample holder corresponds to the ideal scenario, since any family of planes can be placed in the Bragg position". In practice, sample holders often only include one of the two cradles Xi and X2- As a result, the adjustment of the orientation of the family of planes is approximate. [Pg.124]

Other peaks ean appear if the ineidenee angle is such that other planes are approximately in the Bragg position, or if part of a film is comprised of randomly oriented grains. [Pg.288]


See other pages where Bragg position is mentioned: [Pg.477]    [Pg.40]    [Pg.101]    [Pg.163]    [Pg.223]    [Pg.256]    [Pg.96]    [Pg.111]    [Pg.51]    [Pg.51]    [Pg.435]    [Pg.37]    [Pg.27]    [Pg.363]    [Pg.54]    [Pg.386]    [Pg.128]    [Pg.268]    [Pg.1016]    [Pg.30]    [Pg.36]    [Pg.52]    [Pg.83]    [Pg.87]    [Pg.110]    [Pg.159]    [Pg.161]    [Pg.169]    [Pg.183]    [Pg.219]    [Pg.288]    [Pg.293]    [Pg.295]    [Pg.296]   
See also in sourсe #XX -- [ Pg.70 , Pg.294 ]




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Bragg

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