Potential surface of hydrogen and its diffusion on the (100) surface of B.C.C. metals

• Published in: Journal of the less-common metals 1982-01, Vol.88 (2), p.371-378
• Main Authors: Kambara, T., Takanashi, M., Gondaira, K.I., Isshiki, Y.
• Format: Article
• Language: English
• ISSN: 0022-5088
• DOI: 10.1016/0022-5088(82)90245-4

The vibrational states of an adsorbed hydrogen atom and the host metal atoms are described on the basis of the self-consistent Einstein model where the equivalent atoms are treated as harmonic oscillators of the same frequency and their equilibrium positions and the frequency are determined selfconsistently by taking the interatomic interaction into account. Formulae for the determination of the vibrational frequency and the equilibrium position of an adsorbed hydrogen atom are derived in which the relaxation of the position of the host atoms around the adatom is taken into account. The frequency and equilibrium position are calculated for the case of adsorption on the (100) surface of a niobium crystal at various temperatures by using the calculated protonic potential. Reasonable results are obtained. The transition rate of a hydrogen atom between two neighbouring adsorption sites is calculated on the basis of the tunnelling mechanism. The rate obtained is so small that the tunnelling mechanism cannot be responsible for the surface diffusion of the hydrogen atom.