排序方式: 共有2条查询结果,搜索用时 0 毫秒
1
1.
13C-observe REDOR and θ-REDOR experiments for recovering the 13C–2D dipolar interaction during MAS NMR are compared. It is found that limited 2D RF power may severely compromise the performance of the REDOR experiment whereas the θ-REDOR experiment can be designed to work well. Results are presented for an isolated 13C–2D spin pair with a large deuterium quadrupolar coupling constant and for a 13C coupled to three methyl deuterons undergoing fast methyl group rotation. 相似文献
2.
Jinlei Cui David L. Olmsted Anil K. Mehta Mark Asta Sophia E. Hayes 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(13):4254-4260
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 13C–1H distances is exploited along with DFT determinations of the 13C tensor of carbonates (CO32?). Nearby 1H nuclei perturb the axial symmetry of the carbonate sites in the hydrated carbonate mineral, hydromagnesite [4 MgCO3?Mg(OH)2?4 H2O]. 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 13C{1H} REDOR and 13C 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. 相似文献
1