Atomic structure of alkali metal (Li, Na, K) adsorbed Ge(111)-(3x1) surfaces

We have studied the atomic structure of alkali metal (AM) adsorbed Ge(111)-(3x1) surfaces using the pseudopotential and density-functional theory. Our total-energy calculations for Li, Na, and K demonstrate that the AM/Ge(111)-(3x1) surfaces have the same ground-state structure as the AM/Si(111)-(3x1) 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.open1119sciescopu