架状硅酸盐矿物的Raman光谱研究

RAMAN SPECTRA OF FRAMEWORK SILICATE MINERALS

分别测定了架状硅酸盐天然矿物正长石、方钠石和霞石的Raman光谱,利用Materials Studio3.0软件对上述3种矿物的Raman振动频率进行计算,分析他们的简正振动模式,确定了3种矿物的Raman特征谱峰的归属,分析了铝对架状硅酸盐Raman光谱的影响。结果表明:在架状硅酸盐结构中,700～800cm–1区间内出现的谱峰是Al—O振动的表现,800～1200cm–1区间的谱峰是硅氧四面体Q4结构单元振动的反映,随着结构中n(Al)/n(Si)(摩尔比)由正长石的1:3变化至方钠石和霞石的1:1,800～1200cm–1波数区间的振动频率有明显的降低(从1126cm–1降至992cm–1),在霞石和方钠石中n(Al)/n(Si)相同,其振动频率稍有变化。说明随着硅氧四面体结构中AlⅣ含量的增加,800～1200cm–1波数区间的振动频率向低频方向迁移,而金属阳离子的种类会影响Raman光谱的振动频率。

The raman spectra of some framework silicate minerals such as orthoclase, sodalite and nephelite were measured, respectively. The Raman frequencies of the three minerals were calculated by Materials Studio 3.0. The result shows that the raman bands in the range of 700–800 cm–1 were attributed to Al—Onb symmetric stretching vibrations in framework silicates. The bands of 800–1 200 cm–1 stand for Q4 structure unit in silicon-oxygen tetrahedra. When n（Al）/n（Si） （mole ratio） changes from 1：3 in orthoclase to 1：1 in sodalite and nephelite, the vibration wavenumber in spectra decreased remarkably. Although n（Al）/n（Si） is the same in sodalite and nephelite, a slight variation exists in the vibration frequencies. The frequencies in the range of 800–1 200 cm–1 decrease slightly with the increasing of the four-coordinated Al content. The different kinds of cations as network modifiers in framework silicates affect their Raman frequencies.