The mass dependence of diffusion in melts was determined by means of molecular dynamics simulation. The self-diffusion coefficients of Mg and O, with hypothetical masses in the ranges of 1.6 to 360 and 1.0667 to 240amu respectively, were approximately proportional to the atomic mass raised to the -0.1 power for Mg at 3000 to 6000K and to the -0.091 power for O at 6000K. The diffusivity mass dependence in the melt was smaller than in gas phase and was consistent with previous calculations for melts of rare gases and alkali halides. This, together with theoretical considerations, suggested that the diffusivity mass dependence in a melt was small and that this was probably also true of a silicate melt.

Isotopic Effects on Diffusion in MgO Melt Simulated by the Molecular Dynamics (MD) Method and Implications for Isotopic Mass Fractionation in Magmatic Systems. Tsuchiyama, A., Kawamura, K., Nakao, T., Uyeda, C.: Geochimica et Cosmochimica Acta, 1994, 58[14], 3013-21