The theory of diffuse scattering of X-rays by a molecular crystal

1964 ◽  
Vol 280 (1380) ◽  
pp. 1-22 ◽  
Keyword(s):  
Molecular Crystal ◽  
Diffuse Scattering ◽  
Intermolecular Forces ◽  
X Rays ◽  
Frequency Distributions ◽  
Thermal Diffuse Scattering ◽  
X Ray ◽  
X Ray Scattering ◽  
Modes Of Vibration ◽  
Thermal Diffuse

The theory of diffuse X-ray scattering by a molecular crystal is given, it being stressed that the modes of vibration causing scattering are in general mixed translational and librational. The theory is applied to an idealized model of hexamethylenetetramine, making use of the elastic constants and the Raman frequency to determine some of the molecular interaction constants. Dispersion curves are calculated from which frequency distributions are obtained. These compare well with experimental data. The thermal diffuse scattering is calculated and compared with experiment, and with the predictions of more approximate theories. The similarity between all of these suggests that very careful measurement of X-ray intensities will be necessary before conclusions can be drawn about intermolecular forces in crystals.

Determination of phonon dispersion relations by X-ray thermal diffuse scattering

2005 ◽  
Vol 220 (12) ◽  
Author(s):  
Ruqing Xu ◽  
Tai C. Chiang
Keyword(s):  
General Theory ◽  
Diffuse Scattering ◽  
Phonon Dispersion ◽  
Dispersion Relations ◽  
X Rays ◽  
Thermal Diffuse Scattering ◽  
X Ray ◽  
Thermal Diffuse ◽  
Phonon Dispersion Relations

AbstractThermal diffuse scattering (TDS) of X-rays from crystals contains information on phonons. This paper reviews the general theory of TDS and some recent experiments aimed at further developing TDS into a useful and efficient method for studying phonon dispersion relations.

A study of the local atomic structure in Hg0.80Cd0.20Te using x-ray diffuse scattering

1993 ◽  
Vol 8 (4) ◽  
pp. 855-863 ◽  
Author(s):  
J.P. Quintana ◽  
J.B. Cohen
Keyword(s):  
Diffuse Scattering ◽  
Volume Measurement ◽  
Lattice Parameter ◽  
Near Neighbor ◽  
Cation Sublattice ◽  
Thermal Diffuse Scattering ◽  
X Ray ◽  
X Ray Scattering ◽  
The Difference ◽  
Thermal Diffuse

The local atomic arrangements in a commercial n-type wafer of Hg0.8Cd0.8Te were investigated by measuring the diffuse x-ray scattering in two volumes in reciprocal space. A change in contrast between the two measurements was achieved by making one volume measurement at 12037 eV and a second volume measurement at 12270 eV, i.e., near the HgLIII edge. The difference between these two measurements yielded intensity only due to Hg–Hg, Hg–Te, and Hg–Cd pair interactions. In all three patterns, peak-like features were apparent at the forbidden Bragg peak positions on thermal diffuse scattering ridges that joined major Bragg reflections; these are primarily attributed to second order displacement effects on the mixed cation sublattice. The first two Warren–Cowley short-range order parameters were determined to be α½½0 = −0.050(26) and α110 = 0.118(35). Simulations of the structure revealed small ordered regions with a preference for 3:1 Hg–Cd near-neighbor configurations. The near-neighbor Hg–Te bonds contract from that calculated from the average crystal's lattice parameter, and this Hg–Te distance is less than the distance in HgTe.

Diffraction Pattern Caused by X-Ray Thermal Diffuse Scattering in Absorbing Perfect Crystal

1988 ◽  
Vol 57 (2) ◽  
pp. 524-534 ◽  
Author(s):  
Yasuji Kashiwase ◽  
Masahiro Mori ◽  
Motokazu Kogiso ◽  
Masayuki Minoura ◽  
Satoshi Sasaki
Keyword(s):  
Diffraction Pattern ◽  
Diffuse Scattering ◽  
Perfect Crystal ◽  
Thermal Diffuse Scattering ◽  
X Ray ◽  
Thermal Diffuse

Practical Aspects of Removing the Effects of Elastic and Thermal Diffuse Scattering from Spectroscopic Data for Single Crystals

2014 ◽  
Vol 20 (4) ◽  
pp. 1078-1089 ◽  
Author(s):  
Nathan R. Lugg ◽  
Melissa J. Neish ◽  
Scott D. Findlay ◽  
Leslie J. Allen
Keyword(s):  
Factor Analysis ◽  
Energy Loss ◽  
Single Crystals ◽  
Electron Energy ◽  
Diffuse Scattering ◽  
Energy Dispersive ◽  
Thermal Diffuse Scattering ◽  
X Ray ◽  
Electron Energy Loss ◽  
Thermal Diffuse

AbstractA method to remove the effects of elastic and thermal diffuse scattering (TDS) of the incident electron probe from electron energy-loss and energy-dispersive X-ray spectroscopy data for atomically resolved spectrum images of single crystals of known thickness is presented. By calculating the distribution of the probe within a specimen of known structure, it is possible to deconvolve the channeling of the probe and TDS from experimental data by reformulating the inelastic cross-section as an inverse problem. In electron energy-loss spectroscopy this allows valid comparisons with first principles fine-structure calculations to be made. In energy-dispersive X-ray spectroscopy, direct compositional analyses such as ζ-factor and Cliff–Lorimer k-factor analysis can be performed without the complications of channeling and TDS. We explore in detail how this method can be incorporated into existing multislice programs, and demonstrate practical considerations in implementing this method using a simulated test specimen. We show the importance of taking into account the scattering of the probe in k-factor analysis in a zone axis orientation. The applicability and limitations of the method are discussed.

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