The impact of electronic correlations on the structural stability and spectral properties of ferrocene and polyferrocene under pressure

In this work, the electronic, spectral, and structural properties of ferrocene and polyferrocene under pressure have been investigated using DFT and DFT+DMFT methods taking into account dynamic electronic correlations. It is found that polyferrocene crystalizes in three different phases with transitions at 80 and 200 GPa. The calculated DFT+DMFT enthalpy of ferrocene and polyferrocene indicates a possibility of ferrocene transitioning into a polymerized phase at about 80 GPa. It is demonstrated that polyferrocene undergoes an insulator-to-metal transition under pressure, closing a gap of 2.45 eV. However, while the insulating state of polyferrocene can be described as a band insulator, the insulator-to-metal transition is found to be caused by a structural transition into a metallic high-pressure phase of polyferrocene which is defined by strongly correlated behavior of Fe ions.