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

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.