Thermodynamic stability and structures of iron chloride surfaces: A first-principles investigation

In this study, we report a comprehensive density functional theory investigation of the structure and thermodynamic stability of FeCl2 and FeCl3 surfaces. Calculated lattice constants and heats of formation for bulk FeCl2 and FeCl3 were found to be in relatively good agreement with experimental measurements. We provide structural parameters for 15 distinct FeCl2 and FeCl3 surfaces along the three low-index orientations. The optimized geometries for all surfaces are compared with analogous bulk values. Ab initio atomistic thermodynamic calculations have been carried out to assess the relative thermodynamic stability of FeCl2 and FeCl3 surfaces under practical operating conditions of temperatures and pressures. The FeCl2 (100-Cl) surface is found to afford the most stable configuration at all experimentally accessible gas phase conditions.