Atomic mean-square displacements and the critical-voltage effect in cubic solid solutions

Shirley, C. G.; Fisher, R. M.

doi:10.1080/01418617908239278

Cited by 27 publications

(1 citation statement)

References 27 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…For example, a two-parameter model which can be used to interpret CVs in substitutional solid solutions is given by Shirley & Fisher (1979), taking into account vibration amplitudes and static displacements (Fox & Shirley, 1983). Indications of covalent bonding in /3'-NiA1 are given by Fox (1985), based on CV measurements.…”

Section: Materials Indexmentioning

confidence: 99%

On the accurate measurement of structure-factor amplitudes and phases by electron diffraction

Spence¹

1993

Acta Cryst Sect A

139

View full text Add to dashboard Cite

A review is given of research into the measurement of crystal structure-factor amplitudes and phases by transmission electron diffraction. Accuracies for amplitudes are commonly a fraction of a percent (after conversion to X-ray structure factors) while phases may now be measured in favorable cases using three-beam electron diffraction to an accuracy of much better than 1 °. Following a brief review of theory, the main techniques are outlined. These include quantitative convergent-beam electron diffraction, the critical-voltage method, the intersecting K_ikuchi-and HOLZ-Iine methods and methods based on weak high-order reflections in wide-angle patterns. Enantiomorphs and polarity are discussed. Summaries are given of measurements of the mean inner potential and of structure factors generally. A brief review of the implications of this work for studies of crystal bonding and ordering in alloys is given, and its use to test ab initio computations of charge density. The mean inner potential is found to be the quantity most sensitive to the bonding distribution of valence electrons and sensitively constrains accurate X-ray structure-factor measurements. Electron diffraction techniques are to be preferred for studies of individual microcrystals or artificially formed structures and for the very accurate measurement of structure-factor phases in acentric crystals with small unit cells.

show abstract

Section: Materials Indexmentioning

confidence: 99%

On the accurate measurement of structure-factor amplitudes and phases by electron diffraction

Spence¹

1993

Acta Cryst Sect A

139

View full text Add to dashboard Cite

show abstract

Positions and Intensities of Regular Reflection Peaks

Krivoglaz¹

1996

X-Ray and Neutron Diffraction in Nonideal Crystals

View full text Add to dashboard Cite

The Critical Voltage Effect in High-Voltage Electron Microscopy

Fisher¹,

Shirley

1981

JOM

Self Cite

View full text Add to dashboard Cite

SUMMARY INTRODUCTIONResearch-oriented metallurgists are generally aware that increasing the accelerating voltage of the electron microscope can result in a significant increase in specimen penetration.1.2 This ability to examine thick specimens in transmission has been utilized extensively to study the detailed features of microstructures developed during transformation, precipitation, and deformation, using either postmortem sectioning or dynamic in-situ observations on prethinned specimens. At accelerating voltages above the displacement threshold for crystals, electrons in the beam are sufficiently energetic to knock atoms from their lattice sites to create vacancies and interstitials. Study of the agglomeration of vacancies to form planar faults or voids has been a major application of the HVEM for a number of years. Finally, advances in electron microscope lens design and painstaking attention to mechanical and electrical stability have led to the development of very high resolution instruments which should produce atomic-level resolution in the near future.All these features of high voltage electron microscopy have been discussed in detail in various AIME symposia on metallography, as well as in previous special editions of Journal of Metals which were devoted to microscopy.3.4 However, there is one additional and unique aspect of highvoltage electron microscopy that is still not generally familiar to materials scientists, namely, the "critical voltage" effect. 5 • B This phenomenon takes its name from the fact that subtle but characteristic changes occur in the image and corresponding electron diffraction patterns from crystals at certain critical voltages which are determined by the composition, structure, temperature, and other specimen factors. Careful determination of the critical voltage (V e ) can provide quantitative information about departures from randomness in lattice site occupancy, i.e., clustering or shortrange order, Debye temperatures, bonding, and charge transfer in alloys. These basic parameters of crystal physics are usually derived from x-ray or neutron scattering studies or elastic wave propagation experiments and are not considered amenable to analysis by electron microscopy.An important advantage of the critical voltage technique over the other experimental methods is that it is not necessary to work with large single crystals, as the mag-

show abstract

Atomic mean-square displacements and the critical-voltage effect in cubic solid solutions

Cited by 27 publications

References 27 publications

On the accurate measurement of structure-factor amplitudes and phases by electron diffraction

On the accurate measurement of structure-factor amplitudes and phases by electron diffraction

Positions and Intensities of Regular Reflection Peaks

The Critical Voltage Effect in High-Voltage Electron Microscopy

Contact Info

Product

Resources

About