High-field multinuclear solid-state nuclear magnetic resonance (NMR) and first principle calculations in MgSO₄ polymorphs

Abstract

A combination of solid state NMR and first principles calculations was applied to obtain 17 O, 25 Mg and 33 S NMR parameters for two polymorphs of anhydrous magnesium sulfate.Working at the very high magnetic field of 21.14 T results in a dramatic improvement of resolution through a reduction of effects of quadrupolar interactions and significant improvement in sensitivity. approach for the refinement of the crystallographic data.

Structural assessment of anhydrous sulfates with high field 33S solid state NMR and first principles calculations

“…S3 †) which, however, is not entirely a symmetry-dictated. 89 The agreement between calculated and experimental parameters for the anisotropic part of the shielding interaction is fair to good, on the whole. As seen in Table 2, the calculated anisotropy, Δσ aniso and asymmetry parameter, η CSA , are within the same order of magnitude as the experimental values.…”

Ab initio crystal structure prediction of magnesium (poly)sulfides and calculation of their NMR parameters

“…From these tests, the uncertainty of the calculated NMR parameters was estimated. The approach itself and the PAW potentials were validated by calculating isotropic chemical shifts and quadrupolar coupling constants for -MgSO 4 , and by comparing the obtained parameters to the parameters known from the literature (Pallister et al, 2011).…”

“…In other words, it may be useful to calculate 25 Mg isotropic chemical shifts and quadrupolar coupling constants. Although 25 Mg nuclei are rather insensitive nuclei with a natural abundance of 10% and with a low magnetogyric ratio, their NMR spectra can be readily measured in high magnetic fields with specialized 'low-gamma' NMR probeheads (Pallister et al, 2009(Pallister et al, , 2011. The NMR parameters for 33 S might be even more interesting than the 25 Mg NMR parameters, but they are significantly more difficult to measure, as the natural abundance of 33 S is much lower, at 0.76%, and the magnetogyric ratio is similarly small to that of 25 Mg nuclei (Pallister et al, 2011;Moudrakovski et al, 2010).…”

A high-resolution natural abundance 33S MAS NMR study of the cementitious mineral ettringite

“…15 Central-transition (CT) enhancement techniques via population transfer have been successfully implemented in 33 S NMR, 17,19 and observation of three crystallographically distinct S sites in ettringite with C Q values of up to 1 MHz was possible at B 0 = 14.1 T. The Carr-Purcell-Meiboom-Gill (CPMG) pulse sequence is known to boost the S/N ratio by accumulating signal intensity into ''spikelets'' and, following its success in signal enhancement of 33 S-enriched disordered silicates, 18 the CPMG pulse sequence has been frequently employed in high-field solid-state 33 S NMR, especially where only a single S site is present. [20][21][22][24][25][26] For example, acquisition using the CPMG pulse sequence at B 0 = 21.1 T has enabled the observation of large C Q values (9 to 16 MHz) for a single S site at natural 33 S abundance. 22,24 First-principles calculations of 33 S NMR parameters accompany many of the latest solid-state 33 S NMR studies 20,[22][23][24][25][26] to predict and guide assignment of the experimental spectra.…”

“…[20][21][22][24][25][26] For example, acquisition using the CPMG pulse sequence at B 0 = 21.1 T has enabled the observation of large C Q values (9 to 16 MHz) for a single S site at natural 33 S abundance. 22,24 First-principles calculations of 33 S NMR parameters accompany many of the latest solid-state 33 S NMR studies 20,[22][23][24][25][26] to predict and guide assignment of the experimental spectra. Prior knowledge of the magnitudes of quadrupolar broadenings, combined with acquisition at high B 0 fields, has been expanding the range of materials accessible for study by experimental solid-state 33 S NMR.…”