  We have investigated Rb adsorption on the Si(100) surface for 0.5 and 1
monolayer coverages using the total energy method with norm-conserving
pseudopotentials. For 2$\times$1 reconstruction at 1 ML coverage symmetrized
dimers are found to be energetically more favorable. On the other hand, half a
ML coverage is found to have symmetrical dimers only for the most stable
adsorption model. All possible surface-adatom configurations have been
considered in the calculations to find which adsorption sites are energetically
favored. In addition to the structural properties, the interface is
investigated electronically for the work function and surface states. The
results are discussed and compared with the existing experimental findings.
