Isotope effect in perfect and imperfect hydrogenized palladium

The low-pressure hydrogen isotope effect is investigated in imperfect elect ro-deposited Pd materials and compared with that in perfect Pd crystals. Un like in perfect crystals, in strongly disordered crystalline materials the isotope effect is pressure-dependent. In some samples it increases and in o ther samples decreases with pressure. For perfect crystals a theory is deve loped whose results, obtained without any adjustable parameters, agree with experimental data with an accuracy exceeding 2% in the entire temperature range (170-1450 K) available for the experiment at present. This theory is used for a semi-phenomenological interpretation of the experimental data fo r electro-deposited materials. (C) 2000 Published by Elsevier Science B.V. All rights reserved.