Trends in hydrogen heats of solution and vacancy trapping energies in transition metals

Heats of solution and impurity-induced lattice relaxations are calculated for hydrogen in all the transition metals. The hydrogen-metal interaction is described using the effective-medium theory and the metal-lattice relaxations are included in a harmonic-continuum model. The authors find that the trends in the heats of solution can be related to the magnitude of the electron density of the interstitial metal. The trends in the hydrogen trapping energies for vacancies are estimated from the difference between the calculated heats of solution and chemisorption energies. A very simple conceptual picture of the hydrogen-metal interaction results, which can easily be extended to treat for instance hydrogen in metal alloys.