Department of Materials and Environmental Chemistry, Stockholm University, Svante Arrhenius väg 16 C, 106 91 Stockholm, Sweden.
Department of Materials and Environmental Chemistry, Stockholm University, Svante Arrhenius väg 16 C, 106 91 Stockholm, Sweden; Centre de RMN Très Hauts Champs de Lyon (UMR5082 - CNRS, ENS Lyon, UCB Lyon 1), Université de Lyon, 5 rue de la Doua, 69100 Villeurbanne, France.
J Magn Reson. 2022 Jul;340:107235. doi: 10.1016/j.jmr.2022.107235. Epub 2022 May 14.
A combination of solid-state NMR methods for the extraction of Na shift and quadrupolar parameters in the as-synthesized, structurally complex NaMnO Na-ion cathode material, under magic-angle spinning (MAS) is presented. We show that the integration of the Magic-Angle Turning experiment with Rotor-Assisted Population transfer (RAPT) can be used both to identify shifts and to extract a range of magnitudes for their quadrupolar couplings. We also demonstrate the applicability of the two-dimensional one pulse (TOP) based double-sheared Satellite Transition Magic-Angle Spinning (TOP-STMAS) showing how it can yield a spectrum with separated shift and second-order quadrupolar anisotropies, which in turn can be used to analyze a quadrupolar lineshape free of anisotropic bulk magnetic susceptibility (ABMS) induced shift dispersion and determine both isotropic shift and quadrupolar products. Combining all these experiments, the shift and quadrupolar parameters for all observed Na environments were extracted and yielded excellent agreement with the density functional theory (DFT) based models that were reported in previous literature. We expect these methods to open the door for new possibilities for solid-state NMR to probe half-integer quadrupolar nuclei in paramagnetic materials and other systems exhibiting large shift dispersion.
本文提出了一种组合固态 NMR 方法，用于提取在 MAS 下合成的结构复杂的 NaMnO 钠离子阴极材料中 Na 位移和四极参数。我们表明，将 Magic-Angle Turning 实验与 Rotor-Assisted Population transfer (RAPT) 相结合，既可以用于识别位移，也可以用于提取其四极耦合的一系列幅度。我们还证明了基于二维单脉冲（TOP）的双剪切卫星跃迁魔角旋转（TOP-STMAS）的适用性，展示了如何产生具有分离位移和二阶四极各向异性的光谱，进而可用于分析无各向异性体磁共振（ABMS）诱导的位移展宽的四极线宽，并确定各向同性位移和四极产物。结合所有这些实验，提取了所有观察到的 Na 环境的位移和四极参数，与之前文献中报道的基于密度泛函理论（DFT）的模型非常吻合。我们希望这些方法为固态 NMR 在顺磁材料和其他表现出大位移分散的系统中探测半整数四极核开辟新的可能性。
