First principles description of atomic gold chains in Ge(001)

We have performed density-functional theory calculations, including the spin-orbit correction, to investigate atomic gold chains on Ge?001?. A set of 26 possible configurations of the Au/Ge(001) system with c(4x2?) and c(8x2) symmetries is studied. Our data show that the c?4 ? 2? order results in the lowest energy, which is not in direct agreement with recent experiments. Using total-energy calculations, we are able to explain these differences. We address the electronic band structure and apply the Tersoff-Hamann approach to correlate our data to scanning-tunneling microscopy (STM) We obtain two highly competitive structures of the atomic Auchains for which we report simulated STM images in order to clarify the composition of the experimental Au/G(001) surface.