Abstract. In this study, the diffuse pattern and path of hydrogen in transition metal rhodium are investigated by the first-principles calculations. Density functional theory is used to calculate the system energies of hydrogen atom occupying different positions in rhodium crystal lattice. The results indicate that the most stable position of hydrogen atom in rhodium crystal lattice locates at the octahedral interstice, and the tetrahedral interstice is the second stable site. The activation barrier energy for the diffusion of atomic hydrogen in transition metal rhodium is quantified by determining the most favorable path, i.e., the minimum-energy pathway for diffusion, that is the indirect octahedral-tetrahedral-octahedral (O-T-O) pathway, and the activation energy is 0.8345eV.
IntroductionResearch into the reaction of hydrogen with metals has attracted much attention because of potential applications as effective hydrogen storage materials [1], Ho K M et. al [2] studied the metal-hydrogen interactions in NbH by first-principles total energy calculations. And the transition metal-hydrogen systems have also attracted considerable interest for the unfilled d orbitals. Antonov V E [3] discussed the phase transformations, crystal and magnetic structures of high-pressure hydrides of d-metals, and obtained the conclusions that the high-pressure technique had been most effective in hydrogenation of the group VI-VIII transition metals, neither of which except Pd forms hydrides at low hydrogen pressures, and the hydrides formed at high pressures were shown to have close-packed metal sublattices with fcc, hcp or double hcp structures, in which hydrogen occupied octahedral interstitial positions. Then Pronsato M E et. al [4] investigated the electronic and bonding properties of iron monohydride using tight-binding method. We [5,6] had investigated the structural, electronic and magnetic properties of RhH alloy and PdHx with both cubic and tetrahedral structures based on abinitio total energy calculations.Hydrogen diffusion and migration in metals are important aspects to determine the behavior of hydrogen in metals. The diffusion of hydrogen in metals or alloys are also investigated by scientific workers. Diffusion of hydrogen in the α-phase Pd system was investigated by electrochemical methods [7], and the concentration of hydrogen in the metal was gradually increased by control of the electrode potential. The dissolution and diffusion behaviors of hydrogen in copper were investigated based on first-principles calculations in combination [8]. The adsorption and diffusion of hydrogen on ordered Ni 3 Fe(111) surface and in the bulk were studied by first-principles calculations based on density functional theory [9]. The hydrides of Rh were synthesized at the Institute of Solid State Physics, Russian Academy of Sciences for the first time [10,11], and RhH had a NaCl-type crystal structure with H atoms occupying every octahedral site in the face -centered cubic of rhodium lattice with the parameter a =4.010 Å. In this work, ...