Temperature-Dependent Diffusion Coefficients from ab initio Computations: Hydrogen in Nickel

Wimmer, Erich ; Wolf, Walter ; Sticht, Jurgen ; Saxe, Paul ; Geller, Clint ; Najafabadi, Reza ; Young, George

Knolls Atomic Power Laboratory

关键词: Diffusion;    Trapping;    Nickel;    08 Hydrogen;    Phonons;   

DOI  :  10.2172/881301
RP-ID  :  LM-06K021
RP-ID  :  DE-AC12-00SN39357
RP-ID  :  881301

美国|英语

来源: UNT Digital Library

【 摘 要 】

The temperature-dependent mass diffusion coefficient is computed using transition state theory. Ab initio supercell phonon calculations of the entire system provide the attempt frequency, the activation enthalpy, and the activation entropy as a function of temperature. Effects due to thermal lattice expansion are included and found to be significant. Numerical results for the case of hydrogen in nickel demonstrate a strong temperature dependence of the migration enthalpy and entropy. Trapping in local minima along the diffusion path has a pronounced effect especially at low temperatures. The computed diffusion coefficients with and without trapping bracket the available experimental values over the entire temperature range between 0 and 1400 K.