Self-consistent screening of diatomic molecules in an electron gas

We use density-functional theory to calculate the electronic density induce d by a diatomic molecule in a free-electron gas, as well as the embedding e nergy. We perform the calculations for two molecules, Hz and LM. We study t he dependence of the results on parameters such as the internuclear distanc e 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 t he induced density of levels. We show that the response of the medium is se nsitive to the presence of an electric-dipole moment in the isolated molecu le. 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].