Various properties of Pd3Ag/TiAl membranes from density functional theory

• Atomic configuration has a decisive effect on interface cohesion.
• Cohesion properties of Pd3Ag/TiAl interfaces are calculated.
• H diffusion between surface layer and inter-site is more favorable.
• H diffusion has a small effect to reduce interface cohesion of Pd3Ag/TiAl.
• Pd3Ag/TiAl membrane is a good candidate for hydrogen permeation.

First principles calculation reveals that the Pd3Ag/TiAl interface structure terminated with Pd atoms at the top of the octahedral interstitials of TiAl possesses higher interface strength and better thermal stability than other interface structures, which should be fundamentally due to a stronger chemical bonding formed in the interface. Calculation also shows that hydrogen diffusion between surface layer and inter-site seems energetically more favorable than diffusion within the surface layer, and that the small energy barrier suggests the easy diffusion of hydrogen across the Pd3Ag/TiAl interface. Moreover, hydrogen diffusion would have a small effect to increase the interface energy and decrease the interface strength. The calculated results are in good agreement with experimental observations in the literature, and demonstrate that the Pd3Ag/TiAl membranes should be a good candidate for hydrogen permeation.