SelfConsistent Model of Hydrogen Chemisorption
Abstract
The chemisorption of a hydrogen atom on a transitionmetal surface is treated theoretically on the basis of the Anderson Hamiltonian in HartreeFock approximation, which includes the interelectronic interaction within the 1s orbital. Oneelectron theory is shown to be inadequate for this problem. The localized states which may occur are discussed. A simple expression for the chemisorption energy ∆E is obtained, and a variational method is given for obtaining its selfconsistent value. The metal eigenfunctions enter ∆E only through a function ∆(∊), and the foregoing results are exemplified and applied when this function is semielliptical. When the band is halffilled, a single analytic formula for the oneelectron part of ∆E is obtained, in accord with the KohnMajumdar theorem. With some further assumptions, ∆E and the charge on the atom are calculated for adsorption on Ti, Cr, Ni, and Cu. The values of the hopping integral between the 1s orbital and a neighboring metal d orbital required to fit the experimental ∆E are found to be similar and are reasonable. The correct prediction that ∆E_{Ni}>∆E_{Cu} is believed to be significant. A suggestive correlation is found between observations of catalytic orthopara hydrogen interconversion on PdAu alloys and a rigidband calculation of ∆E.
 Publication:

Physical Review
 Pub Date:
 February 1969
 DOI:
 10.1103/PhysRev.178.1123
 Bibcode:
 1969PhRv..178.1123N