Phase stability and thermodynamic properties of FeS polymorphs

We present a Hubbard-corrected density functional theory investigation of FeS polymorphs based on the quasi-harmonic theory of lattice vibrations. We show that the first temperature transition of troilite FeS cannot involve the MnP-type FeS phase, as sometimes reported in the literature, while the sequence of polymorphs in the pressure range 0–100 GPa at room temperature supports the experimental observations. Although with some differences in the critical pressures, our ab initio phase diagram is in line with those derived from X-ray diffraction studies. The thermodynamic properties of troilite FeS are in good agreement with those measured, which lends support to the accuracy of our predictions for the other FeS phases that are less accessible experimentally.