scholarly journals Local Electronic Structure in AlN Studied by Single-Crystal 27Al and 14N NMR and DFT Calculations

Molecules ◽  
2020 ◽  
Vol 25 (3) ◽  
pp. 469 ◽  
Author(s):  
Otto E. O. Zeman ◽  
Igor L. Moudrakovski ◽  
Carsten Hartmann ◽  
Sylvio Indris ◽  
Thomas Bräuniger
Keyword(s):  
Chemical Shift ◽  
Dft Calculations ◽  
Single Crystal ◽  
Coupling Constants ◽  
Quadrupolar Coupling ◽  
Quadrupole Coupling ◽  
Local Electronic Structure ◽  
Optical Alignment ◽  
Experimental Values ◽  
Optimized Geometries

Both the chemical shift and quadrupole coupling tensors for 14 N and 27 Al in the wurtzite structure of aluminum nitride have been determined to high precision by single-crystal NMR spectroscopy. A homoepitaxially grown AlN single crystal with known morphology was used, which allowed for optical alignment of the crystal on the goniometer axis. From the analysis of the rotation patterns of 14 N ( I = 1 ) and 27 Al ( I = 5 / 2 ), the quadrupolar coupling constants were determined to χ ( 14 N ) = ( 8.19 ± 0.02 ) kHz, and χ ( 27 Al ) = ( 1.914 ± 0.001 ) MHz. The chemical shift parameters obtained from the data fit were δ i s o = − ( 292.6 ± 0.6 ) ppm and δ Δ = − ( 1.9 ± 1.1 ) ppm for 14 N, and (after correcting for the second-order quadrupolar shift) δ i s o = ( 113.6 ± 0.3 ) ppm and δ Δ = ( 12.7 ± 0.6 ) ppm for 27 Al. DFT calculations of the NMR parameters for non-optimized crystal geometries of AlN generally did not match the experimental values, whereas optimized geometries came close for 27 Al with χ ¯ calc = ( 1.791 ± 0.003 ) MHz, but not for 14 N with χ ¯ calc = − ( 19.5 ± 3.3 ) kHz.

Density Functional Theory Studies of Bonding in Complexes H3N···XY of Ammonia and Dihalogen Molecules: A Comparison with Experimental Results from Rotational Spectroscopy

2002 ◽  
Vol 57 (6-7) ◽  
pp. 537-543 ◽  
Author(s):  
O. Kh. Poleshchuk ◽  
A. C. Legona
Keyword(s):  
Density Functional ◽  
Natural Bond Orbital ◽  
Coupling Constants ◽  
Rotational Spectroscopy ◽  
Charge Redistribution ◽  
Functional Theory ◽  
Quadrupole Coupling ◽  
Nuclear Quadrupole ◽  
Experimental Values

The electron density and nuclear quadrupole coupling constants (NQCC) of the H3N...XY (n a type in Mulliken notation) complexes, (X, Y = F, Cl, Br and I), are analyzed with the aid of density functional calculations. To demonstrate the quality of the calculations, various bond lengths and NQCCs obtained by using the hybrid Becke-Lee-Perdew-Yang functional are compared with the corresponding experimental values determined from rotational spectroscopy. An analysis of the NQCC values and various quantities derived fromthe natural bond orbital approach reveals that the molecular interaction is mainly electrostatic, with probably only a small extent of intermolecular electric charge redistribution on complex formation

scholarly journals NMR Detection of Oxygen Isotopes in TiO2 Single Crystal

1998 ◽  
Vol 53 (6-7) ◽  
pp. 305-308
Author(s):  
M. Tanigaki ◽  
S. Takeda ◽  
K. Matsuta ◽  
Y. Matsumoto ◽  
T. Minamisono ◽  
...  
Keyword(s):  
Single Crystal ◽  
Quadrupole Moment ◽  
Oxygen Isotopes ◽  
Electric Quadrupole ◽  
Coupling Constants ◽  
Quadrupole Moments ◽  
Quadrupole Interactions ◽  
Quadrupole Coupling ◽  
Nmr Signals

Abstract We studied the electric quadrupole interactions of Oxygen isotopes in a TiO2 single crystal. For 13O and 19O nuclei, quadrupole coupling constants were measured by the β-NMR technique, and for the 17O nucleus the FT-NMR technique was utilized. We synthesized a TiO2 single crystal which was enriched in 17O up to 5 atom % to observe NMR signals without any perturbations from impurities. Using the known quadrupole moment of 17O, EFGs at an O site in TiO2 and the quadrupole moments of 13O and 19O were determined.

Radical addition to ruthenocene at low temperatures: characterization of ruthenocenyl radicals by μSR spectroscopy

2018 ◽  
Vol 96 (3) ◽  
pp. 358-362 ◽  
Author(s):  
Iain McKenzie
Keyword(s):  
Dft Calculations ◽  
Spin Relaxation ◽  
Muon Spin ◽  
Transverse Field ◽  
Relaxation Mechanism ◽  
Coupling Constants ◽  
Muon Spin Rotation ◽  
Electron Spin Relaxation ◽  
Spin Resonance ◽  
Experimental Values

The radicals formed by muonium (Mu) addition to ruthenocene at low temperature (4–200 K) have been characterized by transverse field muon spin rotation (TF-μSR) and avoided level crossing muon spin resonance (ALC-μSR) spectroscopy. The structures of the muoniated radicals have been identified by comparing the experimentally measured muon hyperfine coupling constants with values obtained from DFT calculations (UB3LYP/DGDZVP). Mu addition was observed at the ruthenium and at the cyclopentadiene (Cp) rings, both from the exterior and interior directions. Closer agreement between the DFT calculations and the experimental values are obtained if it is assumed the structures of the Mu adducts of the Cp rings are distorted due to interactions with neighbouring molecules. Changes in the ALC-μSR spectra with temperature indicated that the electron spin relaxation rate of the Cp adducts increases with temperature; however, the specific spin relaxation mechanism is unknown.

(CH3)3CCOOSbCl4: Structure Determination by Zeeman Perturbed NQR

1986 ◽  
Vol 41 (1-2) ◽  
pp. 129-133 ◽  
Author(s):  
Maria L. S. Garcia ◽  
Edwin A. C. Lucken
Keyword(s):  
Molecular Structure ◽  
Magnetic Field ◽  
Crystal Structure ◽  
Single Crystal ◽  
Structure Determination ◽  
Organic Ligand ◽  
Coupling Constants ◽  
Zero Field ◽  
Quadrupole Coupling ◽  
Asymmetry Parameters

A single crystal of tetrachloro(0,0-pivaloylato)antimony(V) has been studied at 77 K, byZeeman perturbed 35Cl NQR, using a FT-NQR pulsed spectrometer. The four lines at zero-field, ν1 = 27.6468, ν2= 27.3070, ν3= 25.7341 and ν4= 25.3438 MHz yield eight EFG tensors in themagnetic field, related by a twofold symmetry element in the crystal. The correspondingasymmetry parameters are η1, = 0.134, η2 = 0.13, η3= 0.07, and η4 = 0.09. The molecular structurededuced from the relative orientations of the principal Z-axes of the EFG tensors confirms that thehigher quadrupole coupling constants are associated with the chlorine atoms in equatorial positions,relative to the plane of the organic ligand, as predicted from NQR powder studies. It is concludedthat the crystal structure is monoclinic with two (class m or 2) or four (class 2/m) moleculesper unit cell. The molecular packing is such that the planes formed by equatorial or axial chlorineatoms are approximately at right angles to their symmetry related images.

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