First-Principles Study Of Hydrogen Diffusion In Transition Metal Rhodium

With the rapid development of world economy, issues of energy development and environmental protection have been much noted all over the world. Hydrogen is the most promising clean energy in the twenty-first century. Studies have shown that a lot of metal-hydrogen systems have very important practical value. For example, they could be applied as energy storage material. In the past, present and future, the research on metal-hydrogen system shall be one of the most influential research areas with both experimental and practical significance.Density functional theory plays an important role in the theoretical research on condensed systems. With the improvement of calculation methods, the density functional theory has seen a rapid development. In recent years, with respect to research on the diffusion of hydrogen in metal and other solid bodies, or in metal oxides, calculation method based on the first principles of density functional theory has been used as a supplement to the traditional experiment method.This thesis adopts the first principles based on density functional theory to study the diffusion behavior of the hydrogen atom in face-centered cubic structure of transition metal rhodium. Relevant calculations include:the embedding energy of a hydrogen atom at the interstitial site in face-centered cubic structure of the rhodium metals, and the activation energy of a hydrogen atom in interstitial site of the face centered cubic rhodium metals when diffusing along divergent paths, as well as change of the electronic structure of the hydrogen atom. The calculation results show that the most stable embedding site is the octahedral interstitial location, and the second stable site is the tetrahedral interstitial location, with embedding energies of-2.0411eV and-1.4988eV. It is concluded that the most efficient diffusion path of the hydrogen atom in rhodium metal is the indirect octahedral-tetrahedral-octahedral path, with an activation energy value of0.8345eV. In different diffusion paths, there exist obvious changes of the hydrogen atom in the peak value and the density of states from the starting position to the saddle point.