Fusion Science and Technology / Volume 60 / Number 4 / November 2011 / Pages 1507-1510
Interaction with Materials / Proceedings of the Ninth International Conference on Tritium Science and Technology (Part 2)
The stability of hydrogen atoms trapped in vacancy clusters of a bcc iron structure is investigated by molecular statics calculations of the hydrogen binding energy to these clusters. The configurations having a minimum potential energy are obtained from the relaxation of a large number of different initial atomic configurations. Calculations of hydrogen binding energy to a mono-vacancy illustrate a relatively large gain of energy in trapping up to two hydrogen atoms in a monovacancy and the increasing difficulty to trap additional atoms due to hydrogen mutual repulsion. Comparison with ab-initio reference calculations of the hydrogen binding energy shows good agreement for up to three trapped hydrogen atoms. Based on the calculations conducted on the most stable vacancy-hydrogen complexes containing two to six vacancies, the maximum capacity of hydrogen atoms per vacancy was found to decrease with the size of vacancy cluster. The calculations of hydrogen binding energies to these clusters show that trapping two hydrogen atoms per vacancy is still a particularly favorable process for vacancy clusters.