Structural and dynamic properties of Fe(1-x)Sx melts at core conditions

Earth's core is subjected to conditions of 320-350 GPa and 5000-6500 K. The core is lighter than the density of pure iron by around 5% to 10%. In addition, the density jump between inner and outer core is 4.5%, being too large to be explained by simple solid-liquid phase transitions. Because of this, it has been suggested that the outer and inner core contain a percentage of light elements (5-10wt% and 2-3wt% respectively). These light elements affect processes from core’s dynamics to recrystallization of the inner core. One of the candidates to be part of the core is Sulphur. In this work, we used ab-initio Molecular Dynamic methods to study structural and dynamical properties of liquid Fe_(1-x)S_x alloys with S concentrations from 5.8 to 16wt%. We looked at the behavior of structural properties as a function of x, P and T as well as to provide information on diffusion and viscosity coefficients. A P-V-T equation of state for melts whose S concentration falls within the values for the outer core predicted by the PREM model is reported. We find density values in agreement with other theoretical and experimental results and show that concentrations between 10-12wt% of S agree with the densities expected for the outer core.