We have studied the atomic structure of alkali metal (AM) adsorbed $\mathrm{Ge}\mathrm{}\left(111\right)\mathrm{}-(3\mathrm{}\times 1)$ surfaces using the pseudopotential and density-functional theory. Our total-energy calculations for Li, Na, and K demonstrate that the $\mathrm{AM}/\mathrm{Ge}\mathrm{}\left(111\right)\mathrm{}-(3\mathrm{}\times 1)$ surfaces have the same ground-state structure as the $\mathrm{A}\mathrm{M}/\mathrm{S}\mathrm{i}\mathrm{}\left(111\right)\mathrm{}-(3\mathrm{}\times 1)$ surfaces, which is referred to as the honeycomb-chain-channel model, and show systematic variations in surface bonding geometry over the AM adsorbates. Details of the structural changes are reported and discussed in connection to the questions raised by recent scanning tunneling microscopy and x-ray photoelectron spectroscopy studies.

• Received 23 August 2002

DOI:https://doi.org/10.1103/PhysRevB.66.233301