Fechtelkord M
Institut für Mineralogie, Universität Hannover, Germany.
Solid State Nucl Magn Reson. 2000;18(1-4):70-88. doi: 10.1006/snmr.2000.0012.
High-temperature 33Na MAS NMR experiments up to 873 K for a number of different sodalites (Na8[AlSiO4]6(NO3)2, Na8[AlSiO4]6(NO2)2, Na8[AlSiO4]6I2, Na7.9[AlSiO4]6(SCN)7.9 x 0.5H2O, Na8[AlGeO4]6(NO3)2, and Na7[AlSiO4]6(H3O2) x 4H2O) were carried out. The spectra of the first five sodalites consist of a quadrupolar MAS pattern with different quadrupolar coupling constants. The quadrupolar interaction for the thiocyanate sodalite, the nitrate aluminosilicate, and germanate sodalite decreases strongly passing a coalescence state on heating, while the quadrupolar interaction of the iodide and nitrite sample shows nearly no change. The basic hydrosodalite shows an asymmetric lineshape at room temperature and, between 350 and 370 K, a second line due to the evaporation of cage-water emerges. The linewidth increases with rising temperature. The temperature dependence of the quadrupolar interaction seems to be a function of the sodalite beta-cage expansion. Two conceivable jump mechanisms are proposed for a tetrahedral two-site jump between occupied and unoccupied tetrahedral sites.
对多种不同的方钠石（Na8[AlSiO4]6(NO3)2、Na8[AlSiO4]6(NO2)2、Na8[AlSiO4]6I2、Na7.9[AlSiO4]6(SCN)7.9×0.5H2O、Na8[AlGeO4]6(NO3)2和Na7[AlSiO4]6(H3O2)×4H2O）进行了高达873 K的高温33Na 固体核磁共振实验。前五种方钠石的谱图由具有不同四极耦合常数的四极固体核磁共振模式组成。硫氰酸根方钠石、硝酸铝硅酸盐方钠石和锗酸盐方钠石的四极相互作用在加热时通过聚结态会大幅降低，而碘化物和亚硝酸盐样品的四极相互作用几乎没有变化。碱性水方钠石在室温下呈现不对称线形，在350至370 K之间，由于笼形水的蒸发会出现第二条谱线。线宽随温度升高而增加。四极相互作用的温度依赖性似乎是方钠石β笼膨胀的函数。针对占据和未占据四面体位置之间的四面体双位点跳跃，提出了两种可能的跳跃机制。
