Relationship between Soret coefficient and potential energy distribution in silicate liquids: A molecular dynamics study

We present the results of force field molecular dynamics simulations of calcium aluminosilicate, sodium aluminosilicate, calcium silicate, and sodium silicate liquids under temperature gradient conditions. Non-equilibrium molecular dynamics simulations of these liquids under temperature gradient conditions reproduced the trend reported for Soret coefficients, with network-forming cations having larger coefficients compared with network-modifying ones. We found a linear relationship between the Soret coefficients and the variance of the potential energy distribution of each cation, which corresponds to the activation energy of diffusion. The Soret coefficients of sodium aluminosilicate liquids show a somewhat different behavior compared with that of the other liquids. This behavior could be explained by charge compensation of fourfold-coordinated aluminum species by sodium cations. Further studies of a larger variety of systems will reveal the full details of the relationship between Soret coefficients and microscopic structure/energy distribution, and enable us to estimate the Soret coefficients.