Hartree-Fock-Slater-LCAO implementation of the moderately large-embedded-cluster approach to chemisorption. Calculations for hydrogen on lithium (100)

We discuss the implementation of Pisani’s moderately large-embedded-cluster scheme in the pseudopotential version of the Hartree–Fock–Slater-LCAO method. We confine ourselves to the chemisorption problem and use a finite representation for the substrate. As an illustration of the method, we perform calculations for the on-top adsorption of hydrogen on the unreconstructed lithium (100) surface. Embedding appears to improve the convergence of the electronic structure with cluster size. The computation time needed for cluster calculations is increased by the embedding, but it is still substantially cheaper to use the indented substrate as an embedding medium than to include it directly.