⁴³Ca MQMAS NMR spectra of three silica-based glasses in which Ca²⁺ ions play different structural roles have been collected and processed in order to extract the underlying NMR parameter distributions. The NMR parameters have been interpreted with the help of molecular dynamics simulations and DFT-GIPAW calculations. This synergetic experimental-computational approach has allowed us to investigate the Ca environment, to estimate Ca coordination numbers from MD-derived models, and to push further the discussion about ⁴³Ca NMR sensitivity to the first and second coordination spheres: ⁴³Ca δiso and Ca-O distance can be successfully correlated as a function of Ca coordination number.
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http://dx.doi.org/10.1016/j.ssnmr.2015.04.003 | DOI Listing |
J Chem Phys
December 2024
Department of Chemistry, Ohio State University, 100 West 18th Avenue, Columbus, Ohio 43210, USA.
A simplified theoretical description of multiple-quantum excitation and mixing for nuclear magnetic resonance of half-integer quadrupolar nuclei is presented. The approach recasts the multiple-quantum nutation behavior in terms of reduced excitation and mixing curves through a scaling of the first-order offset frequency by the quadrupolar coupling constant. The two-dimensional correlation of the static first-order anisotropic line shape to the second-order anisotropic magic-angle-spinning (MAS) line shape is utilized to transform the three-dimensional integral over the three Euler angles into a single integral over the dimensionless first-order offset parameter.
View Article and Find Full Text PDFSolid State Nucl Magn Reson
December 2024
Univ. Lille, CNRS, Centrale Lille, Univ. Artois, UMR 8181 - UCCS- Unité de Catalyse et de Chimie Du Solide, F-59000, Lille, France. Electronic address:
Through-space heteronuclear correlation experiments under magic-angle spinning (MAS) conditions can provide unique insights into inter-atomic proximities. In particular, it has been shown that experiments based on two consecutive coherence transfers, H → I → H, like D-HMQC (dipolar-mediated heteronuclear multiple-quantum correlation), are usually more sensitive for the indirect detection via protons of spin-3/2 quadrupolar nuclei with low gyromagnetic ratio. Nevertheless, the resolution is often decreased by the second-order quadrupolar broadening along the indirect dimension.
View Article and Find Full Text PDFFaraday Discuss
January 2025
Université Paris-Saclay, CEA, CNRS, NIMBE, 91191 Gif-sur-Yvette cedex, France.
Solid-state NMR has established itself as a cutting-edge spectroscopy for elucidating the structure of oxide glasses thanks to several decades of methodological and instrumental progress. First-principles calculations of NMR properties combined with molecular-dynamics (MD) simulations provides a powerful complementary approach for the interpretation of NMR data, although they still suffer from limitations in terms of size, time and high consumption of computational resources. We address this challenge by developing a machine-learning framework to boost predictive modelling of NMR spectra.
View Article and Find Full Text PDFDalton Trans
August 2024
University of Siegen, Faculty IV: School of Science and Technology, Department of Chemistry and Biology, Inorganic Materials Chemistry and Center of Micro- and Nanochemistry and Engineering (Cμ), Adolf-Reichwein-Straße 2, D-57076 Siegen, Germany.
Fumed alumina from the combustion of AlCl produced nano particles with specific areas from 30 to 220 m g (BET) which were characterized by powder X-ray diffraction, Al solid-state NMR and transmission electron microscopy. During the short-lived synthesis, highly disordered γ-alumina progressively transforms into a mixture of δ and θ-alumina. For the γ-alumina particles, only for particles with the highest specific area a significant amount of five-coordinated Al can be found which is only partially located in the particle surface.
View Article and Find Full Text PDFBiophys Chem
July 2024
JEOL Ltd., Musashino, Akishima, Tokyo 196-8558, Japan. Electronic address:
High isotropic resolution is essential for the structural elucidation of samples with multiple sites. In this study, utilizing the benefits of TRAPDOR-based heteronuclear multiple quantum coherence (T-HMQC) and a pair of one rotor period long cosine amplitude modulated low-power (cos-lp) pulse-based symmetric-split-t multiple-quantum magic angle spinning (MQMAS) methods, we have developed a proton-detected 2D Cl/H T-HMQC-MQMAS pulse sequence under fast MAS (70 kHz) to achieve high-resolution in the indirect dimension of the spin-3/2 (Cl) nuclei connected via protons. As T-HMQC polarizes not only single-quantum central transition (SQ) but also triple-quantum (TQ) coherences, the proposed 2D pulse sequence is implemented via selection of two coherence pathways (SQ→TQ →SQ and TQ → SQ→TQ) resulting in the Cl isotropic dimension and is superior to the existing double-quantum satellite-transition (DQ) T-HMQC in terms of resolution.
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