Abstract
We have investigated the H2 molecular adsorption on the Ag(111) surfaces. To treat van der Waals (vdW) interaction accurately, we performed first principles calculation based on spin-polarized density functional theory (DFT) with the semiempirical correction term of vdW interaction. We got the value of 36.0 meV as the depth of potential energy with this method. We also found that in-plane diffusion barrier was less than 1.3 meV, and zero-point energy about perpendicular direction to the surfaces was 5.0 meV. Totally, the adsorption energy of H2/Ag(111) was 31.0 meV, which accordingly agreed with experimental value of 25.5 meV. We also calculated the ortho-para H2 conversion rate with the anisotropic potential energy. We found that this anisotropy induced the hindered rotational state, which imposed steric effects and accelerated ortho-para H2 conversion.
