Coverage dependence study of the adsorption of Pd on MoS₂(0 0 0 1)

We present in this paper ab initio total energy calculations for the adsorption of Pd on MoS₂ for coverages of 1/3, 1 and 4/3 of a pseudomorphic monolayer. We show that the Pd layer prefers to be at an hexagonal lattice constant close to the value found in (1 1 1) Pd bulk in agreement with the experimental evidence. For higher coverage the bonding with the molybdenite surface per Pd atom diminishes. However, due to the larger Pd-Pd cohesion energy, the final result is a gain in adsorption energy with respect to the isolated Pd atom. Using the Bader scheme for the electron density analysis, we have studied the characteristics of the bonding between the Pd layer and the surface. We have found no convincing correlation between the Bader's bonding characterization and the calculated adsorption energies.