First principles study of hydrogen atom adsorption and diffusion on Pd₃Ag(1 1 1) surface and in its subsurface

In this article, we obtain the adiabatic potential energy of a hydrogen atom on a Pd₃Ag(1 1 1) surface and in its subsurface by first principles calculations based on the density functional theory. Moreover, we discuss the difference between the behaviors of the hydrogen atom on Pd(1 1 1) and on Pd₃Ag(1 1 1) surfaces by comparing the calculation results. The results show that the potential energy value increases when the hydrogen atom is located at a site where some of the surrounding atoms are Ag atoms. In addition, the potential energy minimum and the energy barrier into the bulk area of Pd₃Ag(1 1 1) surface are lower than those of the Pd(1 1 1) surface. The decrease of these values is caused by the lattice expansion due to Ag alloying.