Effect of spin polarization for hydrogen adsorbed on Si(111)(1x1) surface:First-principles calculations

The role of spin polarization on adsorption of atomic and molecular hydroge n on Si(111)(1 x 1) surface is examined by comparing the results of the loc al spin density approximation (LSD) and those of the local density approxim ation (LDA). A large improvement of the adsorption energies (around 0.8 eV/ H) was found for the H atom adsorbed on Si(111)(1 x 1) surface. The inclusi on of spin polarization reduces the overbinding between the H atom and the silicon surface and its effect is much more pronounced when the H atom is f ar away from the surface. Despite of the large changes in the adsorption en ergies, the main character of the potential energy surface of the H atom on Si(111)(1 x 1) surface is retained. An opposite effect is found in the cha rge-density-transfer map of LSD results as compared to LDA results for the H atom approaching the surface through the H3 path, in which the H atom los es electrons rather than gains electrons from the surface. The fact that th e H atom tends to lose electrons in the silicon bulk has already been repor ted by the experimental studies for the behavior of the H atom in the p-typ e silicon. For the molecular hydrogen on Si(111)(1 x 1) surface, the effect of the spin polarization is so small that it can be neglected. (C) 2000 Jo hn Wiley & Sons, Inc.