Detailed first-principles calculations have been performed on adsorption of closely spaced rows of Mn atoms on Si(1 0 0) (2 x 1). The optimized geometries and adsorption energies have been obtained. For adsorption of a single Mn atom on Si(1 0 0), binding at the subsurface site below the Si surface dimmer is the most stable adsorption site. For two Mn atoms adsorption models, we found that the h and i sites are the energetically most favorable structure. The magnetic moment of b site is 3.642 mu(B) which is the largest in all possible surface-adatom configurations. We also found that the silicon surface is metallic for the coverages of 0.5 and 1 ML. (C) 2009 Elsevier B. V. All rights reserved.