NMR Database for Minerals

By Xianyu Xue
First created: 2007.2.22; Last revised 2009.11.3.


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1H NMR

1H NMR Database (pdf)(last updated: Nov. 3, 2009)

Explanations
The 1H chemical shift shows good correlation with the hydrogen bonding distance for moderate and strong hydrogen bonds, and thus 1H NMR is a useful tool for the determination of the latter. In addition, the ranges of hydrogen bond distances and 1H chemical shift vary depending on the type of cations the OH group is bonded to, and thus 1H NMR is often also useful for distinguishing different types of OH groups. Ab intio calculations on properly constructed clusters have been shown to reproduce well the experimentally observed correlation between 1H chemical shift and hydrogen bonding distance.



References


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29Si NMR

29Si NMR database (High-pressure minerals) (pdf) (under construction)

Explanations:
The 29Si NMR chemical shift is sensitive to structural factors such as the coordination number (4,5,6), type of anion (O, S, N, etc), type of next-nearest neighbor (NNN) cations (Si, Al, Mg, etc), and type of connectivities (corner-, edge-, or face- sharing). Therefore, 29Si NMR is a useful tool for revealing the Si coordination, Si-Al-Mg order/disorder, Qn distributions, etc. The known chemical shift ranges for SiO4, SiO5, SiO6 are -60 to -128 ppm, ~-150 ppm, -158 to -221 ppm, respectively. Furthurmore, our recent study has revealed that the 29Si chemical shift of SiO6 is more sensitive to the number and type of NNN cations that are connected by edge-sharing than those by corner-sharing. Although the 29Si chemical shift for tetrahedrally coordinated Si can be reasonably predicted by ab initio cluster calculation method, those of octahedrally coordinated Si should better be calculated with periodic ab initio method, because of the difficulty in creating reasonable clusters.



References


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Copyright: Xianyu Xue