Temperature-dependent diffusion coefficients from ab initio computations: Hydrogen, deuterium, and tritium in nickel

Erich Wimmer, Walter Wolf, Jürgen Sticht, Paul Saxe, Clint B. Geller, Reza Najafabadi, and George A. Young
Phys. Rev. B 77, 134305 – Published 11 April 2008

Abstract

The temperature-dependent diffusion coefficients of interstitial hydrogen, deuterium, and tritium in nickel are computed using transition state theory. The coefficient of thermal expansion, the enthalpy and entropy of activation, and the pre-exponential factor of the diffusion coefficient are obtained from ab initio total energy and phonon calculations including the vibrations of all atoms. Numerical results reveal that diffusion between octahedral interstitial sites occurs along an indirect path via the metastable tetrahedral site and that both the migration enthalpy and entropy are strongly temperature dependent. However, the migration enthalpy and entropy are coupled so that the diffusion coefficient is well described by a constant activation energy, i.e., D=D0exp[Q(RT)], with Q=45.72, 44.09, and 43.04kJmol and D0=3.84×106, 2.40×106, 1.77×106m2s1 for H, D, and T, respectively. The diffusion of deuterium and tritium is computed to be slower than that of hydrogen only at temperatures above 400K. At lower temperatures, the order is reversed in excellent agreement with experiment. The present approach is applicable to atoms of any mass as it includes the full coupling between the vibrational modes of the diffusing atom with the host lattice.

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  • Received 16 November 2007

DOI:https://doi.org/10.1103/PhysRevB.77.134305

©2008 American Physical Society

Authors & Affiliations

Erich Wimmer*, Walter Wolf, Jürgen Sticht, and Paul Saxe

  • Materials Design, Inc., Angel Fire, New Mexico 87710, USA

Clint B. Geller

  • Bechtel Bettis, Inc., West Mifflin, Pennsylvania 15122, USA

Reza Najafabadi and George A. Young

  • Lockheed Martin Corporation, Schenectady, New York 12301-1072, USA

  • *Corresponding author; ewimmer@materialsdesign.com
  • Deceased.

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Issue

Vol. 77, Iss. 13 — 1 April 2008

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