In:
Acta Crystallographica Section A Foundations and Advances, International Union of Crystallography (IUCr), Vol. 71, No. 4 ( 2015-07-01), p. 460-466
Abstract:
This paper reports temperature- and energy-dependent phase shifts of resonant multiple-beam X-ray diffraction in germanium crystals, involving forbidden (002) and weak (222) reflections. Phase determination based on multiple-beam diffraction is employed to estimate phase shifts from (002)-based \{(002)(375)(37\overline{3})\} four-beam cases and (222)-based \{ (222)(\overline{5}3\overline{3})\} three-beam cases in the vicinity of the Ge K edge for temperatures from 20 K up to 300 K. The forbidden/weak reflections enhance the sensitivity of measuring phases at resonance. At room temperature, the resonance triplet phases reach a maximum of 8° for the four-beam cases and −19° for the three-beam cases. It is found that the peak intensities and triplet phases obtained from the (002) four-beam diffraction are related to thermal motion induced anisotropy and anomalous dispersion, while the (222) three-beam diffraction depends on the aspherical covalent electron distribution and anomalous dispersion. However, the electron–phonon interaction usually affects the forbidden reflections with increasing temperatures and seems to have less effect on the resonance triplet phase shifts measured from the (002) four-beam diffraction. The resonance triplet phase shifts of the (222) three-beam diffraction versus temperature are also small.
Type of Medium:
Online Resource
ISSN:
2053-2733
DOI:
10.1107/S2053273315009006
Language:
Unknown
Publisher:
International Union of Crystallography (IUCr)
Publication Date:
2015
detail.hit.zdb_id:
2020844-3
