ISSN:
1600-5724
Source:
Crystallography Journals Online : IUCR Backfile Archive 1948-2001
Topics:
Chemistry and Pharmacology
,
Geosciences
,
Physics
Notes:
Measurements made on convergent-beam patterns from MgO taken near the [001] zone-axis at two fixed temperatures have been studied in detail. Two types of patterns, namely the symmetrical excitation of a single 200 reflexion and the simultaneous excitation of the 200, 020, 220, reflexions were studied, using up to 129 beams in the dynamical calculations. The absorption function, Vih exp (−BiS2), was found to be well defined at the zone axis, allowing separate determination of Vih and Bi. For the pattern for single excitation, Vi0 = 0.6 volt, Vih = 0.14 volt, Bi = B = 0.3, was determined at room temperature. In comparing the two types of pattern at high temperature an increase in Vih of between two and three times was found for the 3-reflexion pattern. This increase, and the more normal value found for the single excitation pattern, seems to accord with other experience that the dynamical increase in Vih, as predicted by Yoshioka and Kainuma, possibly occurs in the vicinity of a many-line intersection of the Kossel pattern but not at the zone axis.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1107/S0567739471000287
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