Dataset Information

Effects of Li Confined Motion on NMR Quadrupolar Interactions: A Combined 7 Li NMR and DFT-MD Study of LiR2 (PO4 )3 (R=Ti or Zr) Phases.

ABSTRACT: Ab initio molecular dynamics (MD) simulations and NMR GIPAW (gauge including projector augmented wave) calculations have been used to analyze the coordination and mobility of Li ions in LiTi2 (PO4 )3 (rhombohedral), LiZr2 (PO4 )3 (triclinic), and LiZr2 (PO4 )3 (rhombohedral) phases. Significant discrepancies are observed between static calculations of 7 Li quadrupolar parameters and experimental values. The dynamical origin of this disagreement is demonstrated by incorporating in the calculations thermal vibrations and local motion of atoms with MD simulations. For LiTi2 (PO4 )3 , the quadrupolar constant associated with Li ions grows with temperature because the local symmetry of the system decreases, whereas for the Zr phases, the quadrupolar constant decreases because thermal vibrations reduce the anisotropy of the interaction. Finally, for both Zr phases, MD yields Li distributions that compare well with disorder reported from diffraction studies.

SUBMITTER: Diez-Gomez V

PROVIDER: S-EPMC7079065 | biostudies-literature | 2020 Mar

REPOSITORIES: biostudies-literature

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Publications

Effects of Li Confined Motion on NMR Quadrupolar Interactions: A Combined 7 Li NMR and DFT-MD Study of LiR2 (PO4 )3 (R=Ti or Zr) Phases.

Diez-Gómez Virginia V de Andres Pedro L PL Sanz Jesús J

ChemSusChem 20200130 5

Ab initio molecular dynamics (MD) simulations and NMR GIPAW (gauge including projector augmented wave) calculations have been used to analyze the coordination and mobility of Li ions in LiTi2 (PO4 )3 (rhombohedral), LiZr2 (PO4 )3 (triclinic), and LiZr2 (PO4 )3 (rhombohedral) phases. Significant discrepancies are observed between static calculations of 7 Li quadrupolar parameters and expe ...[more]

PMID: 31872959

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Project description:Quadrupolar solid-state NMR carries a wealth of structural information, including insights about chemical environments arising through the determination of local coupling parameters. Current methods can successfully resolve these parameters for individual sites using sample-spinning methods techniques applicable to quadrupolar I ≥ 1 nuclei, provided second-order central transition broadenings do not exceed by much the spinning rate. For large quadrupolar coupling (C Q) values, however, static acquisitions are often preferable, leading to challenges in extracting local structural information. This study explores the use of two-dimensional QUadrupolar Isotope Correlation SpectroscopY (QUICSY) experiments as a means to increase the NMR spectral resolution and enrich the characterization of quadrupolar NMR patterns under static conditions. QUICSY seeks to correlate the solid-state NMR powder line shapes for two quadrupolar isotopes belonging to the same element via a 2D experiment. In general, two isotopes of the same element will have different nuclear quadrupole moments, gyromagnetic ratios, and spin numbers but essentially identical chemical environments. The possibility then arises of obtaining sharp "ridges" in these 2D correlations, even in static samples showing large quadrupolar effects, which lead to second-order line shapes that are several kilohertz wide. Moreover, pairs of quadrupolar isotopes are recurrent in the periodic table and include important elements such as 35,37Cl, 69,71Ga, 79,81Br, and 85,87Rb. The potential of this approach is explored theoretically and experimentally on two rubidium-containing salts: RbClO4 and Rb2SO4. We find that each compound gives rise to distinctive 2D QUICSY line shapes, depending on the quadrupolar and chemical shift anisotropy (CSA) parameters of its sites. These experimental line shapes show good agreement with analytically derived 2D spectra relying on literature values of the quadrupolar and CSA tensors of these compounds. The approach underlined here paves the way toward better characterization of wideline NMR spectra of quadrupolar nuclei possessing different nuclear isotopes.

Dataset Information

Effects of Li Confined Motion on NMR Quadrupolar Interactions: A Combined 7 Li NMR and DFT-MD Study of LiR2 (PO4 )3 (R=Ti or Zr) Phases.

Publications

Effects of Li Confined Motion on NMR Quadrupolar Interactions: A Combined <sup>7</sup> Li NMR and DFT-MD Study of LiR<sub>2</sub> (PO<sub>4</sub> )<sub>3</sub> (R=Ti or Zr) Phases.

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