Cui Jinlei, Olmsted David L, Mehta Anil K, Asta Mark, Hayes Sophia E
Department of Chemistry, Washington University in St. Louis, 1 Brookings Drive, Campus Box 1134, St. Louis, MO, 63130, USA.
Department of Materials Science and Engineering, University of California, Berkeley, Berkeley, CA, USA.
Angew Chem Int Ed Engl. 2019 Mar 22;58(13):4210-4216. doi: 10.1002/anie.201813306. Epub 2019 Feb 20.
Solid-state NMR measurements coupled with density functional theory (DFT) calculations demonstrate how hydrogen positions can be refined in a crystalline system. The precision afforded by rotational-echo double-resonance (REDOR) NMR to interrogate C- H distances is exploited along with DFT determinations of the C tensor of carbonates (CO ). Nearby H nuclei perturb the axial symmetry of the carbonate sites in the hydrated carbonate mineral, hydromagnesite [4 MgCO ⋅Mg(OH) ⋅4 H O]. A match between the calculated structure and solid-state NMR was found by testing multiple semi-local and dispersion-corrected DFT functionals and applying them to optimize atom positions, starting from X-ray diffraction (XRD)-determined atomic coordinates. This was validated by comparing calculated to experimental C{ H} REDOR and C chemical shift anisotropy (CSA) tensor values. The results show that the combination of solid-state NMR, XRD, and DFT can improve structure refinement for hydrated materials.
固态核磁共振测量结合密度泛函理论（DFT）计算，展示了如何在晶体系统中优化氢原子的位置。利用旋转回波双共振（REDOR）核磁共振来精确测定C-H距离，并结合DFT对碳酸盐（CO₃²⁻）的碳张量进行测定。在水合碳酸盐矿物水菱镁矿[4MgCO₃·Mg(OH)₂·4H₂O]中，附近的氢核会干扰碳酸盐位点的轴向对称性。通过测试多种半局域和色散校正的DFT泛函，并将其应用于从X射线衍射（XRD）确定的原子坐标开始优化原子位置，从而找到了计算结构与固态核磁共振之间的匹配。通过比较计算得到的与实验测得的¹³C{¹H} REDOR和¹³C化学位移各向异性（CSA）张量值，对这一结果进行了验证。结果表明，固态核磁共振、XRD和DFT的结合可以改善水合材料的结构优化。
