Determination of electric field gradient parameters in tellurium

1976 ◽  
Vol 54 (16) ◽  
pp. 1692-1698 ◽  
Author(s):  
K. Hamilton ◽  
B. M. Powell ◽  
P. Martel

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.






1999 ◽  
Vol 55 (6) ◽  
pp. 1034-1037 ◽  
Author(s):  
J. Stahn ◽  
A. Pucher ◽  
U. Pietsch ◽  
J. Zellner ◽  
E. Weckert

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.



2000 ◽  
Vol 655 ◽  
Author(s):  
Marc Dietrich ◽  
Jörn Bartels ◽  
Manfred Deicher ◽  
Kristian Freitag ◽  
Vyacheslav Samokhvalov ◽  
...  

AbstractSingle crystalline, ferroelectric BaTiO3 as material with the highest piezoelectric constants among the perovskites with ordered sublattices was implanted with 111In(111Cd). The electric field gradient at the Ti position was measured with perturbed γγ-angular correlation spectroscopy (PAC) while the crystal was exposed to an external electric field. A quadratic dependence could be observed: νQ(E) = (34.8(1) + 0.16(4) E/kV/mm + 0.080(2) E2/kV2/mm2) MHz. Point charge model calculations reproduce the linear change of Vzz, but not the quadratic term. The polarizability of the host ions of BaTiO3 is known to be nonlinear with respect to an electric field. The resulting quadratic shift of the electron density is reflected in the strength of the EFG.



1978 ◽  
Vol 56 (6) ◽  
pp. 678-680 ◽  
Author(s):  
Ronald Y. Dong

It is pointed out that asymmetry in the electric field gradient is required for a correct determination of the order parameter tensor. Expressions for the quadrupole splittings of deuteriomethylene and deuteriomethyl groups are given without assuming axial symmetry in the electric field gradient and in the degree of orientation.



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