Diffusion of hydrogen and deuterium in Ni0.5Fe0.5 alloy -: effect of pressure

The phonon dispersion in the substitutional fcc alloy Ni0.5Fe0.5 has been calculated theoretically by applying Bom-von Karman formalism including interaction upto fifth neighbours. The Mean Square Displacement (MSD) of surrounding host atoms with hydrogen and deuterium interstitials using Green's function technique and scattering matrix formalism are investigated for the temperature range (500 K-1250 K) from normal pressure to 2.5 GPa pressure. The MSD of atoms surrounding the interstitial are found to be smaller than those of host crystal. The diffusion parameters for hydrogen and deuterium are calculated using reaction coordinate technique for the temperature and pressure ranges mentioned above. It is found that the activation energy for hydrogen diffusion is less than that of deuterium diffusion and the diffusivity ratio D-H/D2(H) approaches the value of 1.75 at higher temperatures. The results are compared with the existing results and a good agreement is observed.