A simulation study and theoretical Raman spectra of cryolitic melts

Abstract

In order to study the nature of the liquid phase numerically, we need a computer simulation method which will yield the dynamical properties of the liquid. In this work, the method of Madden et al. (Castiglione, M.; Wilson, M., Madden, P.A. Phys. Chem. Phys. 1999, 1, 165.) was used within a molecular dynamics calculation to obtain the structural properties of liquid Na(3)AlF(6) (Cryolite). In this system, the Al-Al, Al-Na, Al-F and Na-F radial distribution functions and the coordination numbers of the Al(3+) ion are obtained near or above the melting point. We also determined that the systems which are not crystallized are in the liquid phase, by analyzing the diffusion coefficients with temperature changes. The theoretical Raman spectra of the system of interest were calculated by computer simulation and the effect of temperature on the results were examined in detail. The relationship between the bands appearing in the spectra and the vibrational modes of the AlF(6), AlF(5) and AlF(4) complex ions, which are present in these melts is discussed, in order to see how the Raman spectra reflect the coordination structure around the Al(3+) ions.