Experimental determination of electric-field-induced differences in structure-factor phases of the order of 2%

In order to understand the induced electron-density response of covalently bonded materials to an externally applied electric field, the change of structure-factor phases of several weak reflections of GaAs has been measured by three-beam interferences. Using a modulation technique, phase variations of the order of 1° for a field strength of 1 kV mm−1 were determined. Although the statistics of these first experiments are rather poor, the experiment verifies qualitatively the predictions of a semi-empirical bond-charge model. The measured phase variation is the smallest value determined up to now.

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Determination of electric field gradient parameters in tellurium

Canadian Journal of Physics ◽

10.1139/p76-201 ◽

1976 ◽

Vol 54 (16) ◽

pp. 1692-1698 ◽

Cited By ~ 2

Author(s):

K. Hamilton ◽

B. M. Powell ◽

P. Martel

Keyword(s):

Electric Field ◽

Electric Field Gradient ◽

Field Gradient ◽

Inelastic Neutron Scattering ◽

Mean Square Displacement ◽

Inelastic Neutron ◽

Charge Model ◽

Bond Charge ◽

Bond Charge Model

The relative intensities of the Mössbauer doublet in Te have been analysed at 4 K and 80 K by utilizing values of the mean square displacement tensor derived from inelastic neutron scattering measurements. The orientation β of the electric field gradient ellipsoid and its asymmetry parameter η have been determined. At 4 K, β = 90°, η = −0.17 and at 80 K, β = 92°, η = −0.48. A simple 'bond charge' model is proposed in an attempt to understand the discrepancy between these values of the electric field gradient parameters and those obtained theoretically by other authors.

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Theoretical and Experimental Techniques for the Determination of X-ray Anomalous Dispersion Corrections

Australian Journal of Physics ◽

10.1071/ph850371 ◽

1985 ◽

Vol 38 (3) ◽

pp. 371 ◽

Cited By ~ 6

Author(s):

Dudley Creagh

Keyword(s):

Lithium Fluoride ◽

Anomalous Dispersion ◽

Experimental Techniques ◽

X Ray ◽

Bonded Materials ◽

Theoretical Approaches ◽

Covalently Bonded ◽

Theoretical Predictions

Theoretical and experimental techniques for the determination of the X-ray anomalous dispersion corrections f'(w, LI) and fl/(w, LI) are discussed. The results of experiments on metallic, ionic and covalently bonded materials typified by copper and nickel, lithium fluoride, and silicon respectively are compared with the theoretical predictions. Attention is drawn to deficiencies in both the experimental and the theoretical approaches.

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Ab initio cluster calculations of defects in solids

Philosophical Transactions of the Royal Society of London Series A Physical and Engineering Sciences ◽

10.1098/rsta.1992.0107 ◽

1992 ◽

Vol 341 (1661) ◽

pp. 351-360 ◽

Cited By ~ 48

Keyword(s):

Density Functional ◽

Local Density ◽

Rapid Determination ◽

Molecular Solids ◽

Unusual Structure ◽

Bonded Materials ◽

Ionic Systems ◽

Covalently Bonded ◽

Local Density Functional Theory

A method based on local density functional theory is described which leads to the rapid determination of the structure, vibrational and electronic properties of clusters as large as 100-150 atoms. The technique is particularly suitable for molecular solids, covalently bonded materials where the clusters are terminated by hydrogen, and to ionic systems where the termination consists of a set of distributed charges. The strengths and weaknesses of the method are detailed together with an application to the interstitial carbon-oxygen complex in silicon where oxygen is found to be over-coordinated. The good agreement obtained for the vibrational modes of the complex lends support to the unusual structure found.

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