Explanation of neutron diffraction phenomena observed in vibrating piezoelectric crystals

Buras, B.; Giebułtowicz, T. M.; Minor, Władek; Rajca, Andrzej

doi:10.1002/pssa.2210090204

Cited by 17 publications

(8 citation statements)

References 13 publications

(2 reference statements)

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“…[B is also the ratio between sound velocity and neutron velocity component along "r o, a parameter used by Buras et al (1972).] By expressing c in km s-~ and d in nm one has B = 5cd.…”

Section: Optics Of Neutron Diffraction By Vibrating Crystalsmentioning

confidence: 99%

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Vibrating crystals as possible neutron monochromators

Stoica¹,

Popovici²

1984

J Appl Cryst

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“…[B is also the ratio between sound velocity and neutron velocity component along "r o, a parameter used by Buras et al (1972).] By expressing c in km s-~ and d in nm one has B = 5cd.…”

Section: Optics Of Neutron Diffraction By Vibrating Crystalsmentioning

confidence: 99%

“…For this range some numerical results were obtained by the Monte-Carlo method (Buras et al, 1972) and approximate formulae were derived by Mikula et al (1974Mikula et al ( , 1975.…”

Section: The Reflectivity Of Vibrating Crystalsmentioning

confidence: 99%

Vibrating crystals as possible neutron monochromators

Stoica¹,

Popovici²

1984

J Appl Cryst

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“…The region of the wave vectors k participating in simultaneous diffraction may be substantially enlarged if the single crystal is elastically deformed. It is known from the two-wave approximation that the reflected intensity from a sufficiently thick elastically deformed crystal (when the crystal thickness is many times higher than the extinction length) is proportional to the total change of the Bragg angle along the path of the incident neutrons through the crystal (Buras, Giebultowicz, Minor & Rajca, 1972). Usually, this proportionality, which enables the application of the lamellae model, can be observed in the wide scale of deformation.…”

Section: Theoretical Considerationmentioning

confidence: 99%

Multiple Bragg reflections of neutrons in an elastically deformed single crystal

Vrána¹,

Mikula²,

Michalec³

et al. 1981

Acta Cryst Sect A

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the positions for the different models were insignificant, and in all cases the coordinates derived from Guinier data agreed with the corresponding single-crystal results within the e.s.d.'s. The lower precision of the coordinates derived from Guinier data is primarily a consequence of the limited region of reciprocal space which is sampled, sin 0/2 < 0.46 A-l: the precision of the data itself is comparable with that of the singlecrystal data. Temperature factors correlate highly with the absorption corrections and cannot be determined meaningfully from Guinier data: however, the results suggest that the differences between atomic temperature factors may be physically significant, albeit with rather low accuracy.The absorption correction calculated for a uniform specimen proved a poor approximation, doing little if anything to reduce either R w or the magnitude of the overall temperature factor (which is considered to be a measure of uncorrected systematic errors) for the structures refined. In one case, yttrium oxide, the absorption correction with an empirically optimized coefficient did significantly reduce R w and the e.s.d.'s of the parameters: however, the magnitude of the overall temperature factor increased greatly and the optimized absorption coefficient was more than five times the calculated average value, so that the physical significance of this correction is uncertain.In practice, it appears possible in many cases to correct effectively for systematic errors, including specimen absorption, by a single overall temperature factor (which may be either positive or negative) as proposed by Werner et al. (1979). Good agreement between the model and the data was obtained in this way for the three structures studied here. However, in some cases an improved fit, and hence more precise parameter estimates, may be achieved by including a correction of the form given by Sas & de Wolff (1966) for specimen absorption. Both these corrections are of an ad hoc nature, and are not to be considered as the direct physical consequence of thermal or absorption effects. ReferencesInternational Tables for X-ray Crystallography (1974

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“…The theoretical and experimental investigations of neutron diffraction by a vibrating single crystal by Buras, Giebultowicz, Minor & Rajca (1972) and Michalec, Chalupa, Sedlfikovfi., (in these papers the references are given to other previous papers) gave results showing a manifold enhancement of the average value of integrated reflectivity. The average enhancement was reported to be a monotonically increasing function of the vibration amplitude.…”

Section: Introductionmentioning

confidence: 99%