An<i>ab initio</i>study of S-substituted iron–nickel–silicon alloy at the Earth's inner core pressure

The thermodynamic stability of S-substituting Si into a bcc Fe0.80Ni0.05SxSi(0.15−x) random alloy, with x=0.025 n (n=0−− 4), was investigated up to 350 GPa by using an ab initio density functional method based on the full charge density–exact muffin-tin orbital–coherent potential approximation scheme. From the analysis of the calculated Δ H values, we suggest that the FeNiSSi stoichiometry with zero sulphur content always behaves as the most stable system along the whole pressure range of 0–350 GPa. As a general tendency, we found that the alloys with 6.8–8.1 wt.% Si are energetically more stable than those with lower silicon content, thus supporting the dissolution mechanism for the Earth&#x27;s inner core compositional model.