Notizen: Non-empirical Calculation of Quadrupole Coupling Constants in the Hydrogen Bonded System D(OH2)2+

1974 ◽  
Vol 29 (8) ◽  
pp. 1231-1232
Author(s):  
J. Koller ◽  
A. Ažman
Keyword(s):  
Electric Field ◽  
Electric Field Gradient ◽  
Field Gradient ◽  
Coupling Constants ◽  
Interatomic Distances ◽  
Quadrupole Coupling ◽  
Hydrogen Bonded

The electric field gradient at the hydrogen bonded deuteron in D(OH2)2+ is calculated. The results do not indicate relations between the quadrupole coupling constants and the OD or OO interatomic distances.

The Electric Field Gradient at the Site of the Halogen Ion and Structure of Amino Acid Hydrobromides and Hydroiodides

1992 ◽  
Vol 47 (7-8) ◽  
pp. 887-917
Author(s):  
Armin Kehrer ◽  
Shi-qi Dou ◽  
Alarieh Weiss
Keyword(s):  
Electric Field ◽  
Electric Field Gradient ◽  
Field Gradient ◽  
Room Temperature ◽  
Low Frequency ◽  
Coupling Constants ◽  
Coupling Constant ◽  
Resonance Frequencies ◽  
Quadrupole Coupling ◽  
Frequency Coupling

Abstract The 79,81Br and 127I NQR spectra of several hydrobromides, respectively hydroiodides, of amino acides and dipeptides were studied, mostly as functions of temperature in the range 77 < T/K <420. The investigated compounds are: L-Arg • HBr • H2O, L-Cys • HBr • H2O , L - Cys - S - S - L - Cys • 2HBr, ethanolamine • HBr, L-Glu • HBr, L-His • HBr, L-His • 2HBr, L-Ile HBr • H2O , Sar • HBr, (Sar)2 • HBr, L-Val • HBr • H2O , Gly • LiBr, Gly-Gly • LiBr, ethanolamine HI, Sar • HI, (Sar)2 • HI, (Gly)2 • HI, (L-Val)2 • HI, Gly-L-Leu • HI • H2O . A phase transition with hysteresis was observed for L-Val • HBr • H2O (Tc.up = 318 K, Tc.down = 242 K). Two solid phases of Sar • HI have been studied by NQR, one crystallized from melt, the other one from aqueous solution. For three of the title compounds the crystal structure was determined at room temperature: L-His - 2HBr, P212121 , Z = 4, aj pm = 1652, b/pm = 916, c/pm = 721; L-Cys HBr H2O , P212121 , Z = 4, a/pm = 1955, b/pm = 746, c/pm = 550; Gly-L-Leu • HI • H2O , P2X, Z = 2, a / p m = 1289, b/pm = 914, c/pm = 615, ß/° = 99.In most cases the halogen ion in the studied hydrohalides is polycoordinated by hydrogen bonds of the type N - H • • • X⊖ and O - H • • • X⊖ , X = Br, I. The NQR frequencies and, for iodine, the nuclear quadrupole coupling constants depend on this coordination. A low frequency (coupling constant) region is found for pure N - H • • • X⊖ coordination. Replacing one N - H • • • X⊖ bond by O - H • • • X⊖ rises the electric field gradient, EFG, respectively the resonance frequencies. The dependence of the EFG on the hydrogen bond coordination N - H • • • X⊖ plus O - H • • • X⊖ is discussed for the title compounds including information from literature

scholarly journals Theoretical Studies of the Electric Field Gradient in Hexachlorometallates

1988 ◽  
Vol 43 (7) ◽  
pp. 643-650 ◽  
Author(s):  
Dirk Borchers ◽  
Peter C. Schmidt ◽  
Alarich Weiss
Keyword(s):  
Electric Field ◽  
Electric Field Gradient ◽  
Field Gradient ◽  
Central Atom ◽  
Coupling Constants ◽  
Point Charge Model ◽  
Metal Atoms ◽  
Charge Model ◽  
Quadrupole Coupling ◽  
Distorted Octahedra

Abstract The electric field gradient (EFG) at the chlorine site is calculated for cubic compounds of the K2PtCl6-type (space group Fm3m), M2IMIVCl6, where M1 is an alkali metal and MeIV a tetravalent element. In the calculations the total EFG is subdivided into the contribution of the complex [MIVCl6]2-, EFGcomplex, and the contribution of the ions outside the complex, EFGlattice. EFGcomplex is calculated by the local electron density formalism using the MS-Xα-method, and EFGlattice is determined by the point charge model.It is found that EFGcomplex is positive whereas EFGlattice is negative. Including antishielding effects, the magnitude of EFGlattice is about one fourth of EFGcomplex. The trends in the EFG for the various compounds found theoretically are the same as the trends in the experimental nuclear quadrupole coupling constants e2Q q/h. However, the absolute values of EFGtheo are smaller than the values EFGexp deduced from e2Q q/h.For a fixed central atom MIV the (positive) EFGexp is increasing with increasing radii of the cations (and increasing lattice constant). This increase can be understood by an increase of EFGlattice.On the other hand, for fixed cations and different tetravalent metal atoms, the EFG is increasing with increasing electronegativity of the central atom. This can be understood by an increase of EFGcomplex. For distorted octahedra it is found that the change in the EFG due to the distortion is also due to a change in EFGcomplex.

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.

The Intramolecular Electric Field Gradient at the 14N-Nucleus in Monofluoroacetonitrile and an Improved Partial r0-Structure of the Molecule

1988 ◽  
Vol 43 (7) ◽  
pp. 651-656 ◽  
Author(s):  
M. Andolfatto ◽  
H. Krause ◽  
D. H. Sutter ◽  
M. H. Palmer
Keyword(s):  
Electric Field ◽  
Electric Field Gradient ◽  
Ab Initio ◽  
Field Gradient ◽  
Excellent Agreement ◽  
Ab Initio Calculation ◽  
Structural Information ◽  
Coupling Tensor ◽  
Quadrupole Coupling ◽  
Hyperfine Splittings

Abstract The 14N quadrupole coupling tensor in CH2FCN and CD2FCN was determined from the hyperfine splittings of low J rotational transitions to give indirect structural information on the geometry of the CCN chain.The CCN chain turns out to be slightly bent (2° away from F), in excellent agreement with the result of an earlier ab initio calculation.

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.

Nuclear Quadrupole Resonance of Antimony in Ln3Sb5O12 Crystals

1994 ◽  
Vol 49 (6) ◽  
pp. 687-689 ◽  
Author(s):  
A. M. Raevsky ◽  
A. G. Gukalova ◽  
G. K. Semin
Keyword(s):  
Electric Field ◽  
Electric Field Gradient ◽  
Coupling Constants ◽  
Spectral Parameters ◽  
Compression Effect ◽  
Quadrupole Coupling ◽  
Quadrupole Resonance ◽  
Nuclear Quadrupole ◽  
Asymmetry Parameters ◽  
Lanthanide Compression

Abstract Complete 121,123Sb NQR spectra of crystalline rate earth antimonites Ln3Sb5O12 (Ln = La, Nd, Er, Lu) were recorded at 77 K. The quadrupole coupling constants and asymmetry parameters of the electric field gradient were measured. A “lanthanide compression” effect on the antimony NQR was observed. Using relations found for the antimonites under study, the Sb spectral parameters of other lanthanide compounds can be predicted.

Article

1999 ◽  
Vol 77 (11) ◽  
pp. 1973-1983
Author(s):  
Robert W Schurko ◽  
Roderick E Wasylishen ◽  
Scott J Moore ◽  
Luigi G Marzilli ◽  
John H Nelson
Keyword(s):  
Solid State ◽  
Electric Field ◽  
Electric Field Gradient ◽  
Field Gradient ◽  
Nmr Spectra ◽  
Room Temperature ◽  
Coupling Constants ◽  
Spin Coupling ◽  
Magic Angle ◽  
Spin Spin Coupling

Solid-state 31P NMR spectra of two phosphite- and 17 phosphine-substituted cobaloximes have been acquired under conditions of magic-angle spinning (MAS) and cross polarization (CP) at two applied magnetic fields. In the majority of cases, eight-peak multiplets are observed in the 31P CPMAS NMR spectra, arising from one-bond indirect spin-spin coupling to cobalt (spin S = 7/2). The spacings between adjacent peaks gradually increase or decrease from low to high frequency, due to the presence of residual dipolar coupling between the cobalt and phosphorus nuclei. Values of 1J(59Co,31P) were estimated from the spacing between the central peaks of the eight-peak multiplets. For the phosphine-substituted cobaloximes, values of 1J(59Co,31P) range from 225 to 372 Hz, while in the phosphite derivatives this coupling is considerably larger, from 420 to 615 Hz. From comparison with cobaloximes for which the cobalt nuclear quadrupole coupling interaction is fully characterized, the residual dipolar shift, d, and sense of the 31P NMR spectrum can be utilized to infer the electric field gradient (EFG) orientations at the cobalt nucleus in cobaloximes for which such data are unavailable. The magnitudes of 1J(59Co,31P) and d, as well as the sense of the spectra, are shown to be dependent upon the nature of the axially-substituted ligands. Phosphorus-31 CPMAS NMR spectra of several cobaloximes exhibit broad peak shapes at room temperature. Variable-temperature 31P NMR experiments reveal that the cobalt nucleus is effectively self-decoupled at room temperature; however, splittings due to 1J(59Co,31P) were observed in spectra acquired at low temperatures.Key words: solid-state 31P NMR, 59Co-31P spin-spin coupling constants, 59Co electric field gradient tensors, cobaloximes.

Sign in / Sign up

Export Citation Format

Share Document