Electric field gradients in the ionic crystals NaNO2, NaBF4, NaNO3, and Ba(NO3)2

Mäurer, Helmut; Schmidt, Peter; Weiß, Alarich

doi:10.1016/0022-2860(77)80045-8

Cited by 13 publications

(11 citation statements)

References 29 publications

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“…39 The quad-rupole coupling parameters for NaBF 4 (Table 2) are in good agreement with earlier reported parameters (C Q = 1008.4 kHz and Z Q = 0.095) determined from 23 Na single-crystal NMR at 23 1C. 48 Moreover, the 23 Na data determined for NaBH 4 Fig. 3 11 B MAS NMR spectra of the central and satellite transitions for (a) NaBH 4 -NaBF 4 (1 : 0.5, S2) and (b) NaBH 4 -NaBF 4 (1 : 0.5, S2-300) after heating to T = 300 1C for 1 h. The spinning sidebands from the satellite transitions associated with the centerband resonance at 15.5 ppm extend further than the selected spectral region shown in the figure.…”

Section: Thesupporting

confidence: 88%

Hydrogen–fluorine exchange in NaBH4–NaBF4

Rude

Filsø

D’Anna

et al. 2013

Phys. Chem. Chem. Phys.

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a Hydrogen-fluorine exchange in the NaBH 4 -NaBF 4 system is investigated using a range of experimental methods combined with DFT calculations and a possible mechanism for the reactions is proposed. Fluorine substitution is observed using in situ synchrotron radiation powder X-ray diffraction (SR-PXD) as a new Rock salt type compound with idealized composition NaBF 2 H 2 in the temperature range T = 200 to 215 1C. Combined use of solid-state 19 F MAS NMR, FT-IR and DFT calculations supports the formation of a BF 2 H 2 complex ion, reproducing the observation of a 19 F chemical shift at 144.2 ppm, which is different from that of NaBF 4 at 159.2 ppm, along with the new absorption bands observed in the IR spectra. After further heating, the fluorine substituted compound becomes X-ray amorphous and decomposes to NaF at B310 1C. This work shows that fluorine-substituted borohydrides tend to decompose to more stable compounds, e.g. NaF and BF 3 or amorphous products such as closo-boranes, e.g. Na 2 B 12 H 12 . The NaBH 4 -NaBF 4 composite decomposes at lower temperatures (300 1C) compared to NaBH 4 (476 1C), as observed by thermogravimetric analysis. NaBH 4 -NaBF 4 (1 : 0.5) preserves 30% of the hydrogen storage capacity after three hydrogen release and uptake cycles compared to 8% for NaBH 4 as measured using Sievert's method under identical conditions, but more than 50% using prolonged hydrogen absorption time. The reversible hydrogen storage capacity tends to decrease possibly due to the formation of NaF and Na 2 B 12 H 12 . On the other hand, the additive sodium fluoride appears to facilitate hydrogen uptake, prevent foaming, phase segregation and loss of material from the sample container for samples of NaBH 4 -NaF.

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Section: Thesupporting

confidence: 88%

Hydrogen–fluorine exchange in NaBH4–NaBF4

Rude

Filsø

D’Anna

et al. 2013

Phys. Chem. Chem. Phys.

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“…In potassium nitrate, KNO a , the 14 N nuclear quadrupole interaction is difficult to determine by powder methods because of its intermediate strength, which is too weak for direct determination by NQR and too strong for the first-order NMR powder singularities to be visible. The same is true of 39 K, though in that case the quadrupole interaction can be estimated from the (1/2, -1/2) transition second-order line-shape.…”

Section: Introductionmentioning

confidence: 99%

“…The same is true of 39 K, though in that case the quadrupole interaction can be estimated from the (1/2, -1/2) transition second-order line-shape. There is no strong NMR signal from an associated constituent nucleus which would permit a measurement for either 14 N or 39 K by double resonance methods. Accordingly, we have resorted to single-crystal rotation patterns of the quadrupole-perturbed NMR spectra to determine the quadrupole interactions.…”

Section: Introductionmentioning

confidence: 99%

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¹⁴N and ³⁹K Nuclear Quadrupole Coupüng in KNO₃

Bastow

Stuart

1990

Zeitschrift Für Naturforschung A

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The nuclear quadrupole interaction tensors of 14 N and 39 K in potassium nitrate at room temperature have been determined from nuclear magnetic resonance (NMR) rotation studies of single crystals at 9.4 T. Values for the coupling constants and asymmetry parameters at 296 K are 14 N: e 2 qQ/h = 751 kHz, >7 = 0.022; 39 K: e 2 qQ/h = 1326kHz, i/ = 0.171. The temperature dependence, on approaching the order-disorder phase transition near 401 K, is linear.

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“…The ranges we find on the basis of the available material are 72<e<P 22 show. Progress will be possible by considering the detailed geometry of the coordination, bond lengths and angles, calculating or estimating a charge distribution over the atoms N, O, and H and calculating the EFG by an extended point charge model [75]. The latter one has to take into account that we are dealing with solids belonging to some extent to the group of ionic solids.…”

Section: Glycyl-l-leucine Hydroiodide Monohydrate Gly-l-leu • Hi • Hmentioning

confidence: 99%