X-ray diffraction study of anharmonic thermal vibrations in CuCl

Valvoda, V.; Ječný, J.

doi:10.1002/pssa.2210450132

Cited by 23 publications

(7 citation statements)

References 21 publications

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“…This has indeed been found for ZnX where X --S, Se, Te (McIntyre, Moss & Barnea, 1980). Different anharmonic parameters of the cation and anion were only evaluated in the case of the A~B TM compounds near the zinc blende to NaCl phase transition by Harada (1976) for CuBr and by Valvoda & Je~n~, (1978) for CuC1. It is impossible, however, to distinguish between flGa and ~gs with the present method.…”

Section: Discussionmentioning

confidence: 60%

Determination of the anharmonicity constant of GaAs by means of the Bijvoet relation of the weak (666) reflection

Pietsch¹,

Paschke²,

Eichhorn³

1993

Acta Crystallogr Sect B

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As a result of the influence of anomalous dispersion the weak (hhh) and (hhh) reflections of the zinc blende structure differ from each other. At large scattering vectors this difference, described by the Bijvoet relation B, depends solely on the size of the anharmonic force constant /3. It can be determined by measuring B near the K-absorption edge of any constituent. This experiment was performed for the (666) and (666) reflections of GaAs between A = 0.90 and 0.97 A, using synchrotron radiation. Outside the extended X-ray absorption fine-structure spectroscopy region the integrated intensities decrease in a different manner with increasing A for both reflections measured at 'umweganregung' free azimuthal positions. Under the assumption of/3Oa = --/3As and using the measured wavelength dependence of B, the anharmonicity constant is evaluated to /3 = -1.75 (0.15) × 10-17j •-3 which is nearly the same as that for germanium.

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Section: Discussionmentioning

confidence: 60%

Determination of the anharmonicity constant of GaAs by means of the Bijvoet relation of the weak (666) reflection

Pietsch¹,

Paschke²,

Eichhorn³

1993

Acta Crystallogr Sect B

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“…Colella (1971), Barnea, Mclntyre & Moss (1974) and Bilderback & Colella (1976) have observed Bijvoet differences in low-angle reflections, due to bonding in different ZnS-type structures. Mclntyre, Moss, Boehm & Barnea (1975) and Valvoda & Jecny (1978) have reported Bijvoet differences for high-angle reflections where anharmonic effects are appreciable for ZnSe and CuCI respectively.…”

Section: Anomalous Dispersion Effectsmentioning

confidence: 98%

Anharmonic temperature factors, anomalous-dispersion effects and bonding charges in gallium arsenide

Saravanan¹,

Mohanlal²,

Chandrasekaran³

1992

Acta Cryst Sect A

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The introduction of dispersion corrections in the generalized structure-factor expression for the zinc blende structure leads to the breakdown of Friedel's law for all even-index reflections, owing to bonding or anharmonicity in these crystals. A systematic and precise X-ray diffraction intensity measurement has been carried out using a spherical single crystal of gallium arsenide at 300 K. Least-squares refinement of the experimental data yields the Debye-Waller factors nGa= 0.62 (2), BAs----0.49 (2) A, 2 for the harmonic model and BGa ----0"670 (3), BAs = 0"470 (2) A2 and individual anharmonic thermal factors /3Ga = 3"15 (59) X 10 -Is and /3As = 8"92 (182) X 10 -18 J A-3 for the anharmonic model. The residual index for the discrepancy between measured and calculated structure factors in the present work is R = 1.237% for the harmonic model and R = 1.229% for the anharmonic model. The present work reveals excellent agreement in both sign and magnitude of the Bijvoet inequalities for a large number of reflections. Covalent charge transfer has also been deduced from the experimental measurements on a few quasi-forbidden Bragg reflections showing a net transfer of charge from Ga to As.

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“…However, a few X-ray works have also been reported as reviewed by McIntyre et al [l], who have reported anharmonic thermal vibrations in a flat plate ZnSe single I ) Madurai 625021, India. [3] have reported the refinement of individual anharmonic thermal parameters in GaAs,,,,,P,,,,, and CuC1, respectively.…”

Section: Introductionmentioning

confidence: 99%

“…crystal. Mohanlal and Pathinettampadiyan [2] and Valvoda and JeEny [3] have reported the refinement of individual anharmonic thermal parameters in GaAs,,,,,P,,,,, and CuC1, respectively.…”

Section: Introductionmentioning

confidence: 99%

Investigations of Bijvoet Differences and Anharmonicity in Gallium Phosphide

Saravanan

Mohanlal

Chandrasekaran

1991

Physica Status Solidi (b)

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Precise X-ray diffraction intensity data are collected at 300 K using a perfect single crystal sphere of gallium phosphide. The data are firstly analysed assuming a harmonic thermal vibration of atoms. The refined Debye-Waller factors for this harmonic model are B(Ga) = 0.446(0.010) x lo-' nmz and B(P) = 0.507(0.001) x lo-' nm2 with the residual index R = 1.2715%. Then anharmonic thermal vibration effects are included in the structure factor expressions. In the anharmonic model, two additional parameters, the individual anharmonic thermal parameters, are also included in the refinement process.The refined values are j(Ga) = -1.201(0.371) x J nm-3 with R = 1.2646%. The effect of anomalous dispersion on the structure factor is also analysed. It leads to Bijvoet differences between all odd index inverse reflections. The inclusion of anharmonic effects leads to Bijvoet differences between all even index inverse reflections. The measured Bijvoet ratios are in good agreement with the calculated Bijvoet ratios both in sign and magnitude. The individual Debye-Waller factors, the Bijvoet ratios, observed and calculated both, for the harmonic and anharmonic models, are reported.Prazise Rontgenbeugungsdaten werden bei 300 K an einer perfekten Einkristallkugel von Galliumphosphid gewonnen. Die Daten werden zunachst analysiert unter der Annahme harmonischer Schwingungen der Atome. Die angepaI3ten Debye-Waller-Faktoren fur das harmonische Modell sind /l(Ga) = O,446(0,01O)x 10-2nm-2 und p(P) = O,507(0,001)x lo-' nm2 mit Restindex R = 1,2715%.Sodann werden anharmonische thermische Schwingungen in den Ausdrucken fur den Strukturfaktor bei der Anpassung berucksichtigt; die angepaBten Werte sind j(Ga) = -1,201(0,371) x J nm-3 und j(P) = 2,002(0,274) x J nm-3 rnit R = 1,2646%0. Der EinfluB anomaler Dispersion auf den Strukturfaktor wird ebenfalls untersucht; er fiihrt zu Bijvoet-Differenzen zwischen allen Reflexionen mit ungeradem Index. Die Anharmonizitat fiihrt zu Bijvoet-Differenzen zwischen allen Reflexionen von geradem Index. Die gemessenen Bijvoet-Differenzen stimmen nach Vorzeichen und GroBe gut rnit den gerechneten iiberein. Die berechneten und beobachteten Debye-Waller-Faktoren und BijvoetVerhaltnisse werden angegeben, sowohl fur die harmonischen wie anharmonischen Modelle.J nm-3 and j(P) = 2.002(0.274) x

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X-ray diffraction study of anharmonic thermal vibrations in CuCl

Cited by 23 publications

References 21 publications

Determination of the anharmonicity constant of GaAs by means of the Bijvoet relation of the weak (666) reflection

Determination of the anharmonicity constant of GaAs by means of the Bijvoet relation of the weak (666) reflection

Anharmonic temperature factors, anomalous-dispersion effects and bonding charges in gallium arsenide

Investigations of Bijvoet Differences and Anharmonicity in Gallium Phosphide

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