Local structural study of mantle minerals by NMR spectroscopy

核磁共振波谱研究地幔矿物的局部结构

• 批准号: 08454153
• 负责人: KANZAKI Masami
• 金额: $ 2.5万
• 依托单位: Okayama University
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for Scientific Research (B)
• 财政年份: 1996
• 资助国家: 日本
• 起止时间: 1996 至 无数据
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-08454153/
• 关键词: NMR spectroscopy; local structure; molecular orbital method; mantle mineral; high pressure

In order to study local structure of mantle minerals by means of NMR spectroscopy, it is inevitable to know the relationship between NMR chemical shift and local structure. The coordination number of Si and Al by oxygen atoms changes from four to six at mantle transition zone to top of lower mantle. Therefore, the quantitative study of chemical shift due to the coordination change is very important to understand the structure of phases at those depths. In this study, the relationship between chemical shift and local structure is studied by means of ab initio molecular orbital method. For this study, following clusters are used : Si(OH)_4, Si(OH)_5^-, Si(OH)_6^<2->, Al(OH)_4^-, Al(OH)_5^<2->, Al(OH)_6^<3->Si_2O(OH)_6, Si_3O_3(OH)_6, Si_3O_2(OH)_8. From these calculations following results are obtained.(1) NMR chemical shift due to coordination change of Si and Al,(2) Si Chemical shift due to number of bridging oxygens,(3)O chemical shift and NQCC of bridging oxygen due to Si-O-Si angle change.These calculations are quite consistent with available experimental data, and can be used to extract local structural information from observed NMR spectra.In next stage of present study, we will measure the NMR spectra of deep mantle minerals such as spinel, majorite and perovskite. Using the relationship between chemical shift and local structure obtained in this study, we will investigate the distribution of Mg, Si, and Al in octahedral sites of these minerals. From this kind of study, we can evaluate the configurational entropies of minerals, and its effect to phase relations.

为了利用核磁共振波谱研究地幔矿物的局部结构，必须了解核磁共振化学位移与局部结构之间的关系。从地幔过渡带到下地幔顶部，氧原子与Si和Al的配位数从4变为6。因此，对配位变化引起的化学位移的定量研究对于了解这些深度的相结构非常重要。本研究采用从头算分子轨道方法研究了化学位移与局域结构之间的关系。本研究使用以下簇：Si(OH)_4、Si(OH)_5^-、Si(OH)_6^<2->、Al(OH)_4^-、Al(OH)_5^<2 ->、Al(OH)_6^<3->Si_2O(OH)_6、Si_3O_3(OH)_6、Si_3O_2(OH)_8。从这些计算得到以下结果。(1)由于Si和Al的配位变化引起的NMR化学位移，(2)由于桥接氧的数量引起的Si化学位移，(3)由于Si引起的桥接氧的O化学位移和NQCC -O-Si角度变化。这些计算与现有的实验数据非常一致，可用于从观测到的NMR谱中提取局部结构信息。在本研究的下一阶段，我们将测量深部地幔矿物的NMR谱，例如尖晶石、多数石和钙钛矿。利用本研究中获得的化学位移和局部结构之间的关系，我们将研究 Mg、Si 和 Al 在这些矿物的八面体位点中的分布。通过这种研究，我们可以评估矿物的构型熵及其对相关系的影响。

项目成果

Kanzaki, M.: "Ab initio calculation of ^<29>Si NMR chemical shifts for the clusters of Si(OH)_4, Si(OH)_5^- and Si(OH)_5^<-2>." Mineral.Jour.18. 1-8 (1997)

Kanzaki, M.：“从头计算 Si(OH)_4、Si(OH)_5^- 和 Si(OH)_5^<-2> 簇的 ^<29>Si NMR 化学位移。”

Kanzaki,M.: "Activotion energy of H_2O and H_2 diffusions in silica glass : Semi-empitirical molocular orbitel study" Mineralogical Journal. 19・1. 1-7 (1997)

Kanzaki, M.：“二氧化硅玻璃中 H_2O 和 H_2 扩散的活化能：半经验分子轨道研究”《矿物学杂志》19・1（1997）。

Kanzaki, M.: "Activation energy of H_2O and H_2 diffusions in silica gless : Semi-empirical molecular orbital study" Mineralogical Journal. 19. 1-7 (1997)

Kanzaki, M.：“二氧化硅玻璃中 H_2O 和 H_2 扩散的活化能：半经验分子轨道研究”矿物学杂志。

Kanzaki, M., Xue, X., and Stebbins, J.F.: "Phase relations in Na_2O-SiO_2 and K_2Si_4O_9 systems up to 14 GPa and ^<29>Si NMR study of the new high-pressure phases : Implications to the structure of high-pressure silicate glasses." Phys.Earth Plant.Inter.

Kanzaki, M.、Xue, 和 Stebbins, J.F.：“高达 14 GPa 的 Na_2O-SiO_2 和 K_2Si_4O_9 系统中的相关系以及新高压相的 ^<29>Si NMR 研究：对结构的影响

Kanzaki, M.: "Abinitio ^<27>Al NMR chemical shift calculation for the clusters of Al(OH)_4^-,Al(OH)_5^<2-> and Al(OH)_6^<3->" Journal of the Ceramic Society of Japan. 105. 91-92 (1997)

Kanzaki, M.：“Al(OH)_4^-、Al(OH)_5^<2-> 和 Al(OH)_6^<3-> 簇的 Abinitio ^<27>Al NMR 化学位移计算”