LDA theory of the coverage dependence of the local density of states: Li adsorbed on Ru(001)

To understand recent P-decay NMR experiments on Li atoms chemisorbed on a Ru(001) surface, the work-function changes and the local density of states (LDOS) at E-F and at the Li nucleus are determined from first-principles local-density full potential linearized augmented plane wave calculations for three coverages (Theta =1, 0.25, and 0.11) and two possible sites for Li (fcc and hcp). From full structure optimizations by means of total energy and atomic force calculations, both a surface and in-plane relaxation are found, and Li chemisorption site preferences are determined as a function of coverage. The calculated LDOS is constant for low coverage whereas the work function changes substantially-both in very good agreement with the P-decay NMR experiments. In contrast, the LDOS at high coverage is predicted to increase by a factor of 2.