PD DEPOSITS ON NI(111) - A THEORETICAL-STUDY

The ASED-MO method has been used to gather electronic and energetic in formation on Pd deposits on Ni(111) and Pd atom inclusion in the first Ni layer since these model catalysts exhibit a striking catalytic eff iciency towards butadiene hydrogenation. The electronic structure of P d atoms is strongly altered compared with pure Pd. A Pd(4d)-->Pd(5s) e lectronic transfer occurs in the case of the deposit when a slight sim ilar transfer and a charge transfer from Pd to surrounding Ni takes pl ace in the case of the inclusion. Those results are consistent with XP S experimental data. A low density of states, near the Fermi level, is also observed. The optimal geometrical situation for Pd deposits is f ound to be 2D-aggregates (in pseudoepitaxy or pseudomorphy with the un derlying Ni surface, depending on the aggregate size). Small aggregate s (part of the first Ni layer) are found to be the most stable in the case of a Pd inclusion in the Ni with a Pd-Pd distance of 2.64 Angstro m, in agreement with available EXAFS experimental data.