Dissociative chemisorption of perfluoropolyethers above reactive sites on nickel surfaces: a theoretical contribution

Ab initio quantum-chemistry-based calculations of the molecular geometry and stability properties of CF3OCF3, Ni3CF3 and Ni3OCF3 have been performed, to mimic possible reactants and products formed in the dissociative chemisorption of perfluoropolyethers (PFPE) on a nickel surface. Reactive sites of the nickel surface are simulated by a three-atom cluster Ni3, while the part of PFPE relevant for the reaction is modelled by CF3OCF3. Hartree—Fock and MP2 total energies are computed to estimate the enthalpy change (ΔHr0) associated with a possible dissociation of PFPE on the nickel surface. ΔHr0 is compared with the cohesion energy of liquid PFPE to apprehend the way lubrication can be affected when reactive sites are present on a metallic surface. Basis sets are of double zeta quality on light atoms including carbon, while model core potential (MCP), along with double zeta plus polarization auxiliary basis sets, have been used for the heavy nickel atoms.