Distorted-wave approach to reference-beam x-ray diffraction in transmission cases

Shen, Qun

doi:10.1103/physrevb.61.8593

Cited by 40 publications

(13 citation statements)

References 12 publications

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“…This simple equation provides a much-improved theoretical profile for RBD and the results are in excellent agreement [32] with full dynamical calculations. It can therefore be used directly in RBD data analysis to obtain triplet phase values for macromolecular crystals.…”

Section: Introductionsupporting

confidence: 72%

“…These include the following: (i) feasibility experiments on GaAs and lysozyme to show that the RBD effects are visible in both small molecules and proteins [1,2]; (ii) a simple theory for RBD interference intensity and phase dependence [30][31][32]; (iii) a theoretical simulation on crambin to test the feasibility of using the RBD phase data set for a structural solution [35]; (iv) an inverse-beam RBD measurement for enantiomorphic phase determination [36], and (v) a preliminary demonstration of an automated data analysis algorithm to obtain triplet phases in RBD experiments [37].…”

Section: Methodsmentioning

confidence: 99%

“…(2), includes only the interference term in the diffracted intensity and a phase-insensitive magnitude-squared term has been omitted since it is a higher-order term. For a more rigorous description of reference-beam diffraction, an expanded distorted-wave approximation has been developed recently [30][31][32]. This new approach not only provides the best physical interpretation of the RBD process but also yields a quantitative analytical description of the RED intensities that are almost identical to that obtained using the full multi-beam dynamical theory [13].…”

Section: Introductionmentioning

confidence: 95%

“…This means that we have essentially the Laue transmission case in the thin crystal limit in which the distorted-wave amplitudes are given by r0 =cos(AiiG)+isin(ArG) TG isin(AG)/iG where i/o iS a normalized angle parameter and A is the Pendellosung length as defined in the conventional two-beam dynamical theory. With these parameters, it can be shown that the averaged H-diffracted intensity 'H S given precisely by the following expression [32]:…”

Section: Introductionmentioning

confidence: 99%

“…Instead of the Fresnel theory used for surface studies, a two-beam dynamical theory is employed to evaluate the amplitudes r0 and rG of these distorted waves, while the subsequent scattering of these waves is handled by the Born approximation and contains the interference effect. The fmal result is that the diffracted wave field for H reflection recorded in a RBD oscillation image is given by [31,32]:…”

Section: Introductionmentioning

confidence: 99%

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<title>Phase-sensitive data collection in x-ray crystallography using reference-beam diffraction</title>

Shen

Kycia

Dobrianov

et al. 2001

Advances in X-Ray Optics

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We present recent theoretical and instrumentation developments in phase-sensitive x-ray crystallography using a reference-beam data collection technique. The technique is based on the principle of three-beam or multiple-beam interference, but unlike the conventional method where interference profiles are measured one at a time, the reference-beam diffraction technique integrates three-beam diffraction into the popular oscillation method of data collection, and allows parallel recording of many three-beam interference profiles on an area detector simultaneously [1,2]. Complete interference profiles are measured by taking multiple oscillation exposures while stepping through the rocking curve of the reference reflection. Recent developments include a portable five-circle kappa diffractometer designed to be a part of an automated reference-beam oscillation setup, and a simplified three-beam diffraction theory using a distorted-wave approach that can be used in reference-beam data analyses to extract the reflection phases.

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Section: Introductionsupporting

confidence: 72%

Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 95%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

<title>Phase-sensitive data collection in x-ray crystallography using reference-beam diffraction</title>

Shen

Kycia

Dobrianov

et al. 2001

Advances in X-Ray Optics

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Dynamical Diffraction

Shen¹

2002

Characterization of Materials

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Diffraction‐related techniques using x rays, electrons, or neutrons are widely used in materials science to provide basic structural information on crystalline materials. To describe a diffraction phenomenon, one has the choice of two theories: kinematic or dynamical. Kinematic theory assumes that each x‐ray photon, electron, or neutron scatters only once before it is detected. This assumption is valid in most cases for x rays and neutrons since their interactions with materials are relatively weak. This single‐scattering mechanism is also called the first‐order Born approximation or simply the Born approximation. The kinematic diffraction theory can be applied to a vast majority of materials studies and is the most commonly used theory to describe x‐ray or neutron diffraction from crystals that are imperfect. There are, however, practical situations where the higher‐order scattering or multiple‐scattering terms in the Born series become important and cannot be neglected. This is the case, for example, with electron diffraction from crystals, where an electron beam interacts strongly with electrons in a crystal. Multiple scattering can also be important in certain application areas of x‐ray and neutron scattering, as described below. In all these cases, the simplified kinematic theory is not sufficient to evaluate the diffraction processes and the more rigorous dynamical theory is needed where multiple scattering is taken into account. Dynamical diffraction is the predominant phenomenon in almost all electron diffraction applications, such as low‐energy electron diffraction and reflection high‐energy electron diffraction. For x rays and neutrons, areas of materials research that involve dynamical diffraction may include the situations discussed.

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Dynamical Diffraction

Shen

2012

Characterization of Materials

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Distorted-wave approach to reference-beam x-ray diffraction in transmission cases

Cited by 40 publications

References 12 publications

<title>Phase-sensitive data collection in x-ray crystallography using reference-beam diffraction</title>

<title>Phase-sensitive data collection in x-ray crystallography using reference-beam diffraction</title>

Dynamical Diffraction

Dynamical Diffraction

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