High Field ³³S Solid State NMR and First-Principles Calculations in Potassium Sulfates

Abstract

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Recent technique developments and applications of solid state NMR in characterising inorganic materials

“…45 Sc, 69,71 Ga, 63,65 Cu, 93 Nb, 113,115 In, 139 La) where the effective quadrupolar broadening factor (taking into account both (i) the 'raw' second-order quadrupolar broadening factor, determined by the magnetic and quadrupolar moments along with the spin, and (ii) the local electron density 'magnification' of the external EFG as estimated by the Sternheimer antishielding factor. The effective quadrupole broadening factor is then estimated by multiplying factors (i) and (ii) (defined in Table 2 of [5])) for these nuclei is in the range ~25-250 and compares to 0.6 for 11 B and 3.6 for 27 Al.…”

“…The same sensitivity of the SO 4 chemical shift and Q was used in some cement-related systems to distinguish the different sulphate species present, with ettringite having a very different chemical shift and lineshape from gypsum [64]. As soon as the symmetry of the local coordination drops the quadrupolar interaction rises rapidly, a point well illustrated by a series of potassium sulphates where the SO 4 units are bonded differently [65]. In isolated SO 4 Q was only 0.959 MHz, but this rose rapidly to 16.2 MHz in an S 2 O 7 unit.…”

Testing the sensitivity limits of 33S NMR: An ultra-wideline study of elemental sulfur

“…Considering each of these factors, it is perhaps not surprising that the number of published solid-state NMR studies utilizing this nucleus is so small [1][2][3][4][5][6][7][8][9][10][11][12][13][14]. However, after getting off to a very slow start during the 1980s and 1990s [1][2][3], 33 S solid-state NMR seems to be finally gaining some popularity as a useful and informative probe of the structural environment in sulfur-containing compounds [4][5][6][7][8][9][10][11][12][13][14]. This is mainly due to the increasing availability of high field NMR spectrometers (>14.1 T), which reduce the second order quadrupolar broadening of the central (1/2 M À1/2) transition (CT) as well as providing an increased Zeeman polarization.…”

“…The first application of 33 S MAS NMR to non-crystalline materials was a study of isotopically enriched sulfur-doped silicate glasses of geological interest [5], in which the sulfur environments were shown to be sulfate-like by virtue of the observed chemical shifts. Since then, 33 S MAS NMR has been used to study mineral phases such as ettringite [7,9], tetrathiometallates [8], and other systems [6,[10][11][12][13][14]. Other methodological improvements have also been made.…”

“…Signal enhancement techniques such as QCPMG [15] or population transfer experiments (which transfer polarization from the STs to the CT [16]) have been used to boost the signal and reduce experimental times significantly [9,10,[12][13][14]. Finally, much larger C Q values have recently been observed from transition metal disulfides [11] and potassium sulfate phases [14] using a combination of high magnetic field strengths, QCPMG enhancement and the ''frequency stepping" method, in which the broad spectra are acquired in a number of separate sections whose widths are determined by the excitation bandwidth of the pulse sequence used. To date, the largest 33 S C Q measured by NMR is 16.2 MHz [14], with the vast majority of investigations having been restricted to samples with C Q values of around 2 MHz or less.…”