  Inspired by experimental observations of Pt(111) surfaces reconstruction at
the Pt/graphene (Gr) interfaces with ordered vacancy networks in the outermost
Pt layer, the mechanism of the surface reconstruction is investigated by
van-der-Waals-corrected density functional theory in combination with
particle-swarm optimization algorithm and ab initio atomistic thermodynamics.
Our global structural search finds a more stable reconstructed (Rec) structure
than that was reported before. With correction for vacancy formation energy, we
demonstrate that the experimental observed surface reconstruction occurred at
the earlier stages of graphene formation: 1) reconstruction occurred when C60
adsorption (before decomposition to form graphene) for C60 as a molecular
precursor, or 2) reconstruction occurred when there were (partial) hydrogens
retain in the adsorbed carbon structures for C2H4 and C60H30 as precursors. The
reason can be attributed to that the energy gain, from the strengthened Pt-C
bonding for C of C60 or for C with partial H, compensates the energy cost of
formation surface vacancies and makes the reconstruction feasible, especially
at elevated temperatures. In the Rec structure, two Pt-C covalent bonds are
formed per unit cell, which have a great impact on the adsorbed Gr electronic
structures.
