New method for the determination of the sign and magnitude of electric quadrupole splittings. II. The electric field gradient of Co in hcp and fcc Co

1982 ◽  
Vol 25 (3) ◽  
pp. 1529-1534 ◽  
Author(s):  
E. Hagn ◽  
E. Zech
Keyword(s):  
Electric Field ◽  
Electric Field Gradient ◽  
Field Gradient ◽  
Electric Quadrupole ◽  
New Method

NUCLEAR ELECTRIC QUADRUPOLE INTERACTION IN SINGLE CRYSTALS

1952 ◽  
Vol 30 (3) ◽  
pp. 270-289 ◽  
Author(s):  
G. M. Volkoff ◽  
H. E. Petch ◽  
D. W. L. Smellie
Keyword(s):  
Electric Field ◽  
Electric Field Gradient ◽  
Field Gradient ◽  
Electric Quadrupole ◽  
Quadrupole Coupling Constant ◽  
Coupling Constant ◽  
Gradient Tensor ◽  
Absolute Value ◽  
Principal Axes ◽  
Quadrupole Coupling

Pound's theory of the dependence of electric quadrupole splitting of nuclear magnetic resonance absorption lines in a single crystal on the orientation of the crystal in an external magnetic field is extended to cover the case of a crystal with nonaxially symmetric electric field gradient at the site of the nuclei being investigated. It is shown that an experimental study of the angular dependence of this splitting for three independent rotations of the crystal about any three mutually perpendicular axes will yield complete information about the orientation of the principal axes and the degree of axial asymmetry of the electric field gradient tensor at the site of the nuclei, and also will give the absolute value of the quadrupole coupling constant for those nuclei.The authors' experiments on the splitting of the Li7 absorption lines in a single crystal of LiAl(SiO3)2 (spodumene) are described and are used to illustrate the theory. The absolute value of the quadrupole coupling constant for the Li7 nuclei in spodumene is found to be [Formula: see text]. per sec. The axial asymmetry parameter of the field gradient tensor at the site of the Li nuclei is found to be η≡(ϕxx−ϕvv)ϕzz=0.79 ± 0.01. One of the principal axes of this tensor (the y axis corresponding to the eigenvalue of intermediate magnitude) is experimentally found to coincide with the b crystallographic axis of monoclinic spodumene as required by the known symmetry of the crystal. The other two principal axes are in the ac plane, the z axis (corresponding to the eigenvalue ϕzz of greatest magnitude) lying between the a and c axes at an angle of 48° ± 2° with the c axis.

Determination of electric field gradient parameters in tellurium

1976 ◽  
Vol 54 (16) ◽  
pp. 1692-1698 ◽  
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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