When reconstruction comes around: Ni, Cu, and Au adatoms on δ-MoC(001)

The interaction of Au, Cu, and Ni metal atoms with the δ-MoC(001) surface was studied using periodic density functional (DF) calculations to analyze adsorption energies and equilibrium geometries, work functions, atomic charges, projected density of states (PDOS), and shifts of the transition metal d-band center. The atomic adsorption is found to cause an in-plane distortion of the surface, and, besides, the interaction strength turns to be coverage dependent. A lower coverage allows for a better accommodation of the adsorbate, alongside causing a d-band center shift to more negative energies, as shown by plots of the PDOS. Regardless of the coverage, interaction strength diminishes following the order Ni > Cu > Au. Adatom chemical activity can be inferred based on the calculated d-band center; Ni being the most active metal, followed by Cu, and then Au for every coverage studied. This result well correlates with experiments on other transition metal carbides. Atomic adsorption also diminishes surface work function.