Atomic and electronic structure of Bi/GaAs(001)-alpha2(2 X 4)

We report an ab initio pseudopotential calculation for the atomic and electronic structure of Bi/GaAs(001)-alpha2(2 X 4). Three structural models with Bi coverages of Theta = 1/4 are considered, containing one Bi dimer or two Bi-As mixed dimers. According to our calculations for this coverage, the atomic model of the Bi/GaAs(001)-(2 X 4) reconstruction is similar to the alpha2 structure of the clean GaAs(001)-(2 X 4) surface in which the top As dimer is replaced by a Bi dimer. This result is in agreement with the most recent scanning tunneling microscopy work.