Electric Field Gradients in Alkali Halide Molecules

1974 ◽  
Vol 52 (11) ◽  
pp. 2143-2156 ◽  
Author(s):  
Jean-Pierre Laplante ◽  
Andre D. Bandrauk
Keyword(s):  
Electric Field ◽  
Electric Field Gradient ◽  
Field Gradient ◽  
Alkali Halide ◽  
Electric Field Gradients ◽  
Calculated Density ◽  
Proper Understanding ◽  
Hartree Fock ◽  
Field Gradients ◽  
Classical Models

The electric field gradient q has been calculated from Hartree–Fock wavefunctions for the molecules LiF, LiCl, LiBr, NaF, NaCl, NaBr, KF, and KCl. It is found that σ and π electrons behave quite differently. Exchange distortions are of great importance for a proper understanding of σ contributions to q. Polarizations of π electrons into the bonding region are also considerable. These effects are responsible for failures of classical models and are further discussed using calculated density difference diagrams.

Electric Field Gradients for Small Antimony Based Zintl Clusters from Hartree-Fock Investigations

1996 ◽  
Vol 51 (5-6) ◽  
pp. 557-559
Author(s):  
F. Hagelberg ◽  
T.P. Das ◽  
K. G. Weil
Keyword(s):  
Electric Field ◽  
Electric Field Gradient ◽  
Field Gradient ◽  
Structural Changes ◽  
Electric Field Gradients ◽  
Hartree Fock ◽  
Field Gradients ◽  
Valence Electrons ◽  
Zintl Clusters

Abstract Electric Field Gradient (EFG) calculations have been carried out for Antimony based clusters with 20 and with 22 valence electrons. It is shown that EFGs are very sensitive to structural changes of the clusters under study. This feature can be used to demonstrate the validity of the Zintl-Klemm-Busmann principle for these systems through EFG determinations.

F-Tensor Coefficients in Electric Field Gradient Calculations for Non-Coulombic Potentials

1996 ◽  
Vol 51 (5-6) ◽  
pp. 554-556
Author(s):  
M.J. Ponnambalam
Keyword(s):  
Electric Field ◽  
Electric Field Gradient ◽  
Field Gradient ◽  
Electric Field Gradients ◽  
Cubic Crystals ◽  
Field Gradients

Abstract The F-tensor coefficients are useful in evaluating the stress-induced electric field gradients in cubic crystals. These coefficients are derived for the non-Coulombic inter-atomic potentials Gr-n and Ge-br . Interesting differences are pointed out between these results and those for Coulombic potentials.

Field-Swept NMR Spectra of 11B in Pyrex Glass and 93Nb in NbN Perturbed by Quadrupole Interaction

1998 ◽  
Vol 53 (6-7) ◽  
pp. 309-313 ◽  
Author(s):  
H. Yoshida ◽  
H. Nishihara ◽  
S. Yokota ◽  
M. Ohyanagi ◽  
T. Nakaoki
Keyword(s):  
Electric Field ◽  
Electric Field Gradient ◽  
Field Gradient ◽  
Quadrupole Interaction ◽  
Pyrex Glass ◽  
Electric Field Gradients ◽  
Field Gradients ◽  
High Temperature Synthesis ◽  
High Resolution Nmr ◽  
Quadrupole Effect

Abstract NMR experiments of 11B by both field-swept and high-resolution NMR are reported to probe the electric field gradient at boron sites and its distribution in Pyrex glass. Both spectra are successfully interpreted with the same set of parameters. It is stressed that field-swept NMR experiments to observe total powder spectrum can be helpful to get information on electric field gradients and asymmetry pa-rameters if there exist many nonequivalent sites of atoms, since satellite transitions are affected by the larger first-order quadrupole effect. Field-swept NMR of 93Nb in superconducting NbN powder, prepared by self-propagating high-temperature synthesis, is also reported. A very broad field-swept spectrum disturbed by quadrupole interaction has been observed. The spectrum is simulated by assuming distributions in electric field gradient and Knight shift at Nb sites. It is stressed that a combination of experiments at separated frequencies is important.

ELECTRIC FIELD GRADIENTS IN SEMICONDUCTORS AND INSULATORS: EMPIRICAL CORRELATION FOUND IN BINARY OXIDES

1992 ◽  
Vol 06 (28) ◽  
pp. 1819-1825 ◽  
Author(s):  
M. RENTERÍA ◽  
C.P. MASSOLO ◽  
A.G. BIBILONI
Keyword(s):  
Electric Field ◽  
Electric Field Gradient ◽  
Field Gradient ◽  
Near Neighbor ◽  
Coupling Constants ◽  
Local Component ◽  
Binary Oxides ◽  
Field Gradients ◽  
Wide Range ◽  
Data Points

For the first time a well defined correlation between local and lattice contributions of the electric field gradient in semiconductors and insulators is presented. The local component of the electric field gradient in binary oxides, originated in extraionic contributions, is extracted from all quadrupole coupling constants measured in Perturbed Angular Correlation experiments with 111Cd probes. The resulting systematics reveals a linear dependence of the local component over a wide range of ionic efg values, both contributing with opposite signs. The clustering of the data points is explained in terms of the oxygen near neighbor symmetry.

Sternheimer Factors and Electric-Field-Gradient Hyperpolarisabilities for Ions in Crystals

1994 ◽  
Vol 49 (1-2) ◽  
pp. 125-128 ◽  
Author(s):  
P. W. Fowler ◽  
H. M. Kelly
Keyword(s):  
Electric Field ◽  
Electric Field Gradient ◽  
Field Gradient ◽  
Significant Variation ◽  
Ion Pairs ◽  
Lattice Parameter ◽  
Hartree Fock ◽  
Shielding Factor ◽  
Free Ion ◽  
Or Modelling

Abstract Analytic coupled Hartree-Fock calculations of the electric field gradient response properties y (the Sternheimer shielding factor) and e (the dipole-dipole-electric field gradient hyperpolarisability) have been carried out on anions in clusters that simulate that crystal environment. The systems studied are F- in LiF and NaF, Cl- in LiCl and NaCl, O2-in MgO, S2- in MgS, and H- in LiH. Both properties show large reductions from free-ion values and significant variation with lattice parameter, and the results indicate that damped values of anion Sternheimer factors will be necessary in accurate simulation of N Q R data or modelling of properties of ion-pairs.

Quadrupole Coupling in some H-bonded Organic Systems by ab initio Lattice Calculations of Electric Field Gradients

1994 ◽  
Vol 49 (1-2) ◽  
pp. 146-154
Author(s):  
Michael H. Palmer ◽  
John A. Blair-Fish
Keyword(s):  
Electric Field ◽  
Ab Initio ◽  
Bulk Material ◽  
Electric Field Gradients ◽  
Hartree Fock ◽  
Organic Systems ◽  
Field Gradients ◽  
Quadrupole Coupling ◽  
Lattice Calculations ◽  
Distant Neighbour

Abstract We present ab initio Hartree-Fock lattice calculations performed in the unit cell environment, to compute a wave-function and the derived electric field gradients for the bulk material. These calculations differ from cluster calculations by including the effects of more distant neighbour molecules. Examples considered are ammonia, formamide, oxamide, urea, thiourea, uracil, para-banic acid, alloxan, guanidine bicarbonate and melamine.

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