The ground and excited states of PtH and PtH+ by relativistic ab initio electronic structure calculations: A model study for hydrogen chemisorption on platinum surfaces and related photoemission properties

Abstract

Relativistic electronic structure calculations for the ground and excited states of PtH and PtH⁺ are performed using first a spin‐averaged relativistic effective core potential (AREP) at the self‐consistent field (SCF) level and later incorporating the spin dependence at the configuration interaction (CI) level. These calculations lead to several conclusions: (1) Both the 6s and 5d orbitals of Pt interact strongly with the H orbitals, clearly indicating that the bonding involves both 6s and 5d electrons. (2) Correlation energies contribute significantly to the PtH binding energy but have little effect on the force constant. (3) The polarization functions centered on H are much more important than those centered on Pt in affecting the binding energy. (4) The two lowest states ²Δ_5/2 and ²Σ_1/2 are calculated to have almost exactly the same energy; either may be the lower one. The lowest 3/2 state is mixed ²(π+Δ)_3/2 and lies a little higher in energy. (5) Both the first ionization potential and the ionization energy of the H‐like level agree reasonably well with the experimental data. Finally, the absolute binding energy of PtH is 2.45 eV, to be compared with the experimental value of 3.44 eV. The discrepancy is due to our computational limitations.