Computational model for H-H/metal interaction

S. SIMONETTI; F. REY SARAVIA; G. BRIZUELA; A. JUAN

San Jose

Simposio; Hydrogen- Power Theoretical and Engineering Solutions International Symposium; 2011

To achieve the goal of road-ready fuel cell vehicles, great strides must also be made in the studies of metal-H interaction and safety considerations. The interaction between two-hydrogen atoms and a g-Fe structure containing a vacancy was studied using a cluster model and an Atom Superposition and Electron Delocalization theoretical method. For the study of the sequential absorption, the hydrogen atoms were positioned in their energy minima configurations, near the vacancy. The interactions mainly involve Fe 4s - H 1s atomic orbitals. The contribution of Fe 4p and Fe 3d orbitals is much less important. The Fe-Fe bond is weakened as new Fe-H-H and H-H pairs were formed. The effect of H atoms is limited to its first Fe neighbors. The Fe-Fe bond strength decreases with the introduction of the H atoms. Fe-H bonding is achieved at expense of weakening the metal-metal nearest bonds. There is not a real bond between the H atoms but some H-H interaction is observed. The detrimental effect of H atoms on the Fe-Fe bonds can be related to one of the aspect of embrittlement in g-Fe.