Vicinage effects in the energy loss of slow LiH molecules in metals

We study the energy loss of slow LiH molecules moving in a free electron gas. The molecule loses energy along its trajectory due to the excitation of electrons in the medium. The energy loss is obtained from a non-linear treatment of the scattering of electrons off the molecule screened potential. This potential and the total electronic density are calculated with density functional theory. We analyze the vicinage effect, i.e. the difference between the energy loss of the LiH molecule and that of the isolated atoms (Li and H) for two kind of trajectories, parallel and perpendicular to the molecule axis. As the electron density decreases, we find that the energy loss of the molecule is larger than that of the isolated atoms for some particular trajectories. Comparison to the vicinage effect of the H2 molecule and the dipole revels the peculiarity of this behavior.