Adsorption of Pd on MoS2(1000):: Ab initio electronic-structure calculations

We present ab initio total energy calculations of the adsorption energy of one Pd monolayer on MoS2(1000). We consider four different adsorption sites: the Pd atoms on top of Mo, on top of the hole site, on top of the surface S, and on the bridge position halfway between two adjacent S atoms. The largest adsorption energy obtained corresponds to the hexagonal site on top of Mo. The maximum energy difference between adsorption sites is 0.25 eV. Due to the lattice mismatch, a Pd monolayer should be expanded to grow pseudomorphically on this substrate. Comparing the energy difference between the adsorption sites to the energy involved in the expansion of a Pd monolayer, we conclude that Pd will tend not to grow pseudomorphically, in agreement with the experimental evidence. We have also evaluated the changes in the;work function produced by the deposition of the Pd adlayer; we observe a systematic reduction with respect to the clean substrate. [S0163-1829(99)04132-6].