Dynamical behaviors of self-interstitial atoms in tungsten

Abstract

The motion mechanisms and jump rate of single self-interstitial atoms (SIAs) are studied by molecular dynamics simulations and vibration analysis. The migration of SIAs is a sequent transformation between the 〈111〉 crowdion and dumbbell with a 0.027eV energy barrier. A soft mode contributes to this transformation, whose eigenvector shows that the atoms compressed by the SIAs have the largest amplitude. The jump rate of SIAs migration reaches 1Hz at 12K, which suggests that the thermal migration of SIAs dominates the nucleation of SIAs loops below 50K. SIAs rotate between the [111] and its equivalent directions with a 0.668eV energy barrier, which is controlled by a linear combination of libration and stretching mode. Our results show that the long wave phonon induced by the stress field of SIAs plays an important role in the 1D motion of SIAs.