Self-consistent screening of diatomic molecules in an electron gas

We use density-functional theory to calculate the electronic density induced by a diatomic molecule in a free-electron gas, as well as the embedding energy. We perform the calculations for two molecules, Hz and LM. We study the dependence of the results on parameters such as the internuclear distance or the mean electronic density of the medium. We discuss the evolution of the system as the medium electronic density is modified with the help of the induced density of levels. We show that the response of the medium is sensitive to the presence of an electric-dipole moment in the isolated molecule. The electron gas screens the interaction between the two centers of the molecule, but can also play a role in transferring charge between them. We show that the shape of the embedding energy variation can be related with different types of molecular adsorption. [S0163-1829(99)02227-4].