Interaction between Interstitials and α-α' Phase Transition in Metals

Abstract

The electronic contribution to the interaction energy between interstitial solute atoms in transition metals is investigated within the tight-binding approximation. The method permits to study the adsorption of the gas atom in the octahedral sites as well as in the tetrahedral sites. Calculations have been carried out as a function of band-filling, energy level of adsorbed atom, and a general hopping potential V_a between an interstitial atom and the nearest-neighbour host atoms. The 'angular position' dependence on the interaction energy is often weak and the possibility of the interstitial condensation (gas (α)-liquid (α') phase transition) observed in such a Nb-H (or Pd-H) system is discussed. Contact is also made with the dipole-dipole interaction based on the elastic theory.