Evidence for anharmonic interactions in cadmium from elastic X-ray scattering

Merisalo, M.; Peljo, E.; Soininen, J. A.

doi:10.1016/0375-9601(78)90574-1

Cited by 9 publications

(7 citation statements)

References 15 publications

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“…It might be supposed that an anisotropic extinction correction would have an effect on the antisymmetric anharmonic parameter o~33 , and indeed there is some difference between the values refined via models 2 and 4. The value of t133 in cadmium has been found by Merisalo, Peljo & Soininen (1978) from an investigation of the 'quasi-forbidden' reflection 303 to be 81 + 12 eV nm -3. The value of 57 + 16 eV nm -3 obtained with model 4 in the present analysis confirms from independent data the existence of a small value of a33.…”

Section: Resultsmentioning

confidence: 99%

“…This has recently been demonstrated in tetragonal tin, where Merisalo & Jarvinen (1978) determined the parameter for the antisymmetric component in the one-particle potential to be a32 + = (390 + 30) eV nm -3 from a measurement on three quasiforbidden reflections, whereas Field (1978) obtained a value of a32+ = (370 + 40) eV nm -3 from an analysis of Bragg reflection data. In the case of cadmium, there has been a recent estimate of the antisymmetric potential parameter from a measurement on a quasi-forbidden reflection by Merisalo, Peljo & Soininen (1978). Also, a singlecrystal X-ray investigation of cadmium has been carried out by Rossmanith (1978) and a set of structure factors published (Rossmanith, 1978, Supplementary Publication).…”

Section: Introductionmentioning

confidence: 99%

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On anharmonicity in cadmium

Field¹

1982

Acta Cryst Sect A

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Recent X-ray diffraction data on cadmium [Rossmanith (1978). Acta Cryst. A34, 497-500] have been reanalysed using a temperature factor based on an anharmonic one-particle potential to fourth order for the atoms, and values for the anharmonic parameters have been obtained. The fourth-order parameters a40 and f120 are found not to be significantly different from zero, while the other fourth-order parameter Y00 is found to be strongly correlated to the extinction correction and harmonic parameters. The third-order antisymmetric parameter is found to have a value of 57 + 16 eV nm -3, which is in reasonable agreement with a recent measurement. The application of the extinction correction is shown to affect substantially the values for the potential parameters.

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

On anharmonicity in cadmium

Field¹

1982

Acta Cryst Sect A

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“…Earlier diffraction experiments on h.c.p, elements Zn (Merisalo, J/irvinen & Kurittu, 1978) and Cd (Merisalo, Peljo & Soininen, 1978) show that the almost-forbidden reflections are really weak. For magnesium, for which the c/a ratio is nearly ideal, the situation can be expected to be even more unfavourable.…”

Section: Methodsmentioning

confidence: 93%

“…Test experiments carried out on a tin single crystal indicated that use of the previously mentioned techniques considerably reduced the collection time for an almost forbidden reflection compared with using a crystal monochromator (Merisalo, Peljo & Soininen, 1978). The magnesium single-crystal sample was supplied by Metals Research Co.…”

Section: Methodsmentioning

confidence: 99%

“…X-ray and neutron diffraction studies on the first and best known case-the 222 reflection in diamond structures -have demonstrated both non-sphericity of valence-charge density and anharmonicity of thermal vibrations (Roberto & Batterman, 1970;Keating & Nunes, 1971;Bilderback & Colella, 1975). Recently, almost-forbidden reflections have been observed in hexagonal close-packed zinc (Merisalo, J~irvinen & Kurittu, 1978) and cadmium (Merisalo, Peljo & Soininen, 1978), and in tetragonal tin (Merisalo & J~irvinen, 1978). In all these studies the data were interpreted in terms of anharmonicity of lattice vibrations.…”

Section: Introductionmentioning

confidence: 99%

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Anharmonicity of atomic vibrations in magnesium by measurement of almost-forbidden reflections

Järvinen¹,

Soininen²,

Merisalo³

1987

Acta Cryst Sect A

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BRAGG AND DIFFUSE SCATTERING INTENSITIESto believe that Bragg intensities fitted with a split-atom model necessarily correspond to a static distribution of atoms about fractionally occupied sites. In the present model, for example, the atoms are continuously hopping across the potential barrier for T> Tc and even below Tc some hopping occurs until the temperature is low enough for the ordering to be complete. Nevertheless, a split-atom model would give a reasonable fit to the corresponding Bragg scattering [see Mair (1983b), where a split-atom model is used to fit probability densities for a onedimensional analogue of the present data].A CSIRO Cyber 205 grant is gratefully acknowledged.References COWLEY, J. M. (1975 AbstractThe X-ray intensities of almost-forbidden reflections 301 and 303 in a single crystal of magnesium have been measured at 293 K. Effective monochromatization by appropriate electronics was utilized to increase the observability of these weak reflections. The data are interpreted in terms of atomic vibrations by application of a quantum-statistical one-particle formalism that allows anharm0nic contributions to the atomic temperature factor. A value of -0.43 (3)eV~ -3 is obtained for the third-order anharmonic parameter, the negative sign being deduced from the coordination. This outcome is in accordance with earlier results concerning anharmonic vibrations.

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A Reexamination of Diffraction Data on Zinc to Determine Anharmonic Components in the One-Particle-Potential Model

Field

1983

Phys. Stat. Sol. (a)

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A reexamination of three single‐temperature sets of X‐ray and neutron diffraction data on zinc is made in the framework of the one‐particle‐potential (OPP) model to determine anharmonic parameters of the potential. An appropriate OPP for the hexagonal metal zinc is V(u) = V0 + u2 (α20K20 + β00) + u3α33K33 + u4(α40K40 + β20K20 + γ00). The fourth order anharmonic parameters α40, β20 and γ00 are found to be not significantly different from zero. The third order parameter α33 is found to be barely significant with a value with standard error of (330 ± 200) eV nm−3. This is in disagreement with previous analyses on zinc, and reasons for this are discussed. Excellent agreement is found between two of the three data sets for refined values of the harmonic parameters, r.m.s. vibration amplitudes, and Debye temperatures.

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Evidence for anharmonic interactions in cadmium from elastic X-ray scattering

Cited by 9 publications

References 15 publications

On anharmonicity in cadmium

On anharmonicity in cadmium

Anharmonicity of atomic vibrations in magnesium by measurement of almost-forbidden reflections

A Reexamination of Diffraction Data on Zinc to Determine Anharmonic Components in the One-Particle-Potential Model

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