硅酸盐熔体微结构单元的对称伸缩模的拉曼散射系数

Raman scattering coefficients of symmetrical stretching modes of microstructural units in sodium silicate melts

通过一种新开发的模拟计算方法 ,计算了硅酸钠熔体的拉曼谱 ,及其在高频区代表 5种硅氧四面体 (用Qi 表示 ,其中i表示桥氧数 )的特征峰的拉曼散射系数Si,发现成分的变化对 5种Qi 的特征峰的拉曼散射系数的影响非常小 .在此基础上取平均分别得到 :S0 =1,S1 =0 .5 14 ,S2 =0 2 4 2 ,S3=0 0 90和S4 =0 0 15 然后将计算得到的散射系数应用于二硅酸钠熔体的实验谱图的定量分析中 ,得到了该熔体中硅氧四面体单元的分布 .同时从计算与试验谱图的定量解谱中发现 ,钠系硅酸盐熔体谱中Q0 和Q2 的ASS模所产生的散射信号不容忽视 .

Quantitative analysis of Raman spectra of vitreous or molten silicate is always one of the key subjects in some fields, e.g. materials science, geological physics, etc. But there are many difficulties with this analysis, one of which is the determination of Raman scattering coefficient. Not long ago, we developed a new method for the calculation of Raman spectrum of amorphous silicate. Essentially, this method combines the molecular dynamics simulation with wilson's GF matrix method, electro-optical parameter method and bond polarizability model. With this theoretical method, we have studied the Raman scattering coefficients of symmetrical stretching modes of Q(i) in sodium silicate melts, and concluded that these coefficients are independent of composition. Meanwhile, the five values of the coefficients are also given as follows: S-0 = 1, S-1 = 0.514, S-2 = 0.242, S-3 = 0.090 and S-4 = 0.015. In order to apply these quantities to experiments, the Raman spectrum of sodium disilicate melt has been measured and its high-frequency envelope has been deconvolved into three Gaussian bands. Finally, the molar fractions of Q(i) were achieved by dividing the area fractions of the three Gaussian bands by corresponding scattering coefficients. Additionally, combining the results of theoretical calculation and quantitative analysis of experimental spectra, we found that the intensities of anti-symmetrical stretching modes of Q(0) and Q(2) in sodium silicate melts are so strong that they cannot be neglected in the deconvolution process.