Electronic structure calculations of a surface-molecule complex by SCF-scattered wave method

Abstract

The study of interaction of molecules with surfaces is of great current interest with a view to understanding the nature of the surface bond, chemisorption and catalysis. We wish to investi-gate a prototype system-namely the interaction of formaldehyde with a silicon substrate. A “surface-molecule complex” or cluster model concept is used to carry out the electronic structure calculations using an SCF-procedure based on the statistical exchange approximation and muffin-tin potentials. An appropriate cluster consisting of formaldehyde molecule and several silicon atoms was chosen. By comparing the results obtained for this cluster with the electronic energy level structure of the free molecule, it was possible to recognize an “adsorption orbital” which may indicate the formation of a surface bond. The charge distribution on the remaining orbitals of formaldehyde remains essentially unaltered. Similar conclusions have been arrived at by Eastman and Demuth from their photoemission data of hydrocarbons on a nickel surface. © 1974 The Japan Society of Applied Physics.