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

Abstract

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 physi cs, 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. Essentiall y, this method combines the molecular dynamics simulation with wilson's GF matri x method, electro_optical parameter method and bond polarizability model. With t his theoretical method, we have studied the Raman scattering coefficients of sym metrical stretching modes of Qi in sodium silicate melts, and concluded th at these coefficients are independent of composition. Meanwhile, the five values of the coefficients are also given as follows: S0=１, S1=0514, S2=0 242, S3=0090 and S4=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. Fina lly, the molar fractions of Qi were achieved by dividing the area fraction s of the three Gaussian bands by corresponding scattering coefficients. Addition ally, combining the results of theoretical calculation and quantitative analysis of experimental spectra, we found that the intensities of anti_symmetrical stre tching modes of Q0 and Q2 in sodium silicate melts are so strong tha t they cannot be neglected in the deconvolution process.