We report the fabrication and characterization of nanocrystalline Er2O3 thin films, as well as the calculations of interstitial deuterium (D) behaviors in bulk Er2O3 using first-principles calculations based on density-functional theory. Our results show that the prepared Er2O3 thin films possess a regular cubic phase with a phase structure consisting mainly of bulk and grain boundaries. Transport of hydrogen isotopes in bulk is predicted to occur by translocation between empty interstitials (e.g., tetrahedral or octahedral sites), and involves hopping from one empty interstitial to another. The rate-determining process of diffusion and permeation is hydrogen isotope movement from tetrahedral site to octahedral site. Transport of hydrogen isotopes within grain boundaries is predicted to be dominant based on the comparison of D permeability or permeation activation energy between experiments and DFT calculations. At a typical temperature of 873 K, the solubility, diffusion coefficient, and permeability of D in bulk Er2O3 are predicted to be 2.94 x 10(-15) mol m(-3), 3.56 x 10(-10) m(2) s(-1), and 3.68 x 10(-27) mol m(-1) s(-1) Pa-1/2, respectively. (C) 2015 Elsevier B.V. All rights reserved.