scholarly journals The Predictive Power of Different Projector-Augmented Wave Potentials for Nuclear Quadrupole Resonance

Crystals ◽  
2019 ◽  
Vol 9 (10) ◽  
pp. 507 ◽  
Author(s):  
Jaafar N. Ansari ◽  
Karen L. Sauer ◽  
James K. Glasbrenner
Keyword(s):  
Nuclear Quadrupole Resonance ◽  
Density Functional ◽  
Predictive Ability ◽  
Transition Elements ◽  
Field Gradients ◽  
Resonance Frequencies ◽  
Quadrupole Resonance ◽  
Nuclear Quadrupole ◽  
Experimental Values ◽  
Projector Augmented Wave

The projector-augmented wave (PAW) method is used to calculate electric field gradients (EFG) for various PAW potentials. A variety of crystals containing reactive nonmetal, simple metal, and transition elements, are evaluated in order to determine the predictive ability of the PAW method for the determination of nuclear quadrupole resonance frequencies in previously unstudied materials and their polymorphs. All results were compared to experimental results and, where possible, to previous density functional theory (DFT) calculations. The EFG at the 14N site of NaNO2 is calculated by DFT for the first time. The reactive nonmetal elements were not very sensitive to the variation in PAW potentials, and calculations were quite close to experimental values. For the other elements, the various PAW potentials led to a clear spread in EFG values, with no one universal potential emerging. Within the spread, there was agreement with other ab initio models.

An arsenic-75 nuclear quadrupole resonance study of α and β As4S3

1972 ◽  
Vol 25 (11) ◽  
pp. 2291 ◽  
Author(s):  
TJ Bastow ◽  
ID Campbell ◽  
HJ Whitfield
Keyword(s):  
Thermal Expansion ◽  
Temperature Dependence ◽  
Nuclear Quadrupole Resonance ◽  
Electrostatic Field ◽  
Β Phase ◽  
Field Gradients ◽  
Α Phase ◽  
Resonance Frequencies ◽  
Quadrupole Resonance ◽  
Nuclear Quadrupole

The nuclear quadrupole resonance frequencies of 75As in the α and β forms of As4S3 have been measured at 77, 195, and 293 K. The frequencies at 77 K were: α phase 64.87 65.94 79.56 MHz β phase 65.42 67.16 79.65 MHz An analysis is presented in terms of Townes-Dailey theory and of the temperature dependence in terms of Bayer-Brown theory. The differences in frequencies of the α and β forms were attributed to the effect of electrostatic field gradients, estimated by lattice sums. Allowance must be made for the thermal expansion of the lattice to obtain a consistent interpretation.

scholarly journals Rapid Survey of Nuclear Quadrupole Resonance by Broadband Excitation with Comb Modulation and Dual-Mode Acquisition

2020 ◽  
Author(s):  
Yuta Hibe ◽  
Yasuto Noda ◽  
K. Takegoshi ◽  
Kazuyuki Takeda
Keyword(s):  
Nuclear Quadrupole Resonance ◽  
Frequency Comb ◽  
Spin Dynamics ◽  
Signal Acquisition ◽  
Dual Mode ◽  
Rapid Scan ◽  
Resonance Frequencies ◽  
Wide Range ◽  
Quadrupole Resonance ◽  
Nuclear Quadrupole

Nuclear Quadrupole Resonance (NQR) provides spectra carrying information as to the electric-field gradient around nuclei with a spin quantum number I > 1/2 and offers helpful clues toward characterizing the electronic structure of materials of chemical interest. A major challenge in NQR is finding hitherto unknown resonance frequencies, which can scatter over a wide range, requiring time consuming repetitive measurements with stepwise frequency increments. Here, we report on an efficient, two-step NQR protocol by bringing rapid-scan and frequency-comb together. In the first step, wideband excitation and simultaneous signal acquisition, both realized by a non-adiabatic, frequency-swept hyperbolic secant (HS) pulse with comb modulation, offers a clue for the existence/absence of the resonance within the frequency region under investigation. When and only when the sign of the resonance has been detected, the second step is implemented to compensate the limited detection bandwidth of the first and to unambiguously determine the NQR frequency. We also study the spin dynamics under the comb-modulated HS pulse by numerical simulations, and experimentally demonstrate the feasibility of the proposed scheme, which is referred to as RApid-Scan with GApped excitation with Dual-mode Operation (RASGADO) NQR<br>

Nuclear Quadrupole Resonance Studies of Chelated Antimony Complexes. Part III. The Carboxylates: RCO2SbCl4

1986 ◽  
Vol 41 (1-2) ◽  
pp. 179-185
Author(s):  
Claudine Gerard-Dion ◽  
Joyce Rupp-Bensadon ◽  
Edwin A. C. Lucken
Keyword(s):  
Phase Change ◽  
Nuclear Quadrupole Resonance ◽  
Chlorine Atoms ◽  
Resonance Frequencies ◽  
Quadrupole Resonance ◽  
Antimony Complexes ◽  
Quantitative Basis ◽  
Nuclear Quadrupole ◽  
The Difference

The 35Cl, 121Sb and 123Sb resonance frequencies for seventeen tetrachloro(carboxylato)antimony V compounds, RCO2SbCl4, are reported. The results confirm the difference in the effects of the substituent on the equatorial chlorine atoms and the axial chlorine atoms of the SbCl4 group, previously remarked in Parts I and II of this series, and this effect has been put on a more quantitative basis by correlating the observed frequencies with the pK’s of the corresponding acids.The compounds with R = isopropyl and R = cyclopropyl both show a phase change in the region of 140 K which may correspond to reorientation of the substituent about the R - CO2 axis.

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