Cluster Model for Electronic Structure and Bonding Mechanism of Interstitial Hydrogen in Iron Series Transition Metals

Electronic structure calculations have been carried out for small clusters of iron series transition metals containing an interstitial hydrogen atom by the discrete variational Xα method. The hydrogen-metal bonding level is formed below the bottom of the d band. The electron transfer from metal to hydrogen occurs, though the additional electron by hydrogenation occupies the 3 d hole to raise the Fermi level. The covalent bonding between H 1 s and metal 3 d is rather strong in all cases. Change in metal-metal bond by interstitial hydrogen is also significant in the bonding mechanism.