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arXiv · 1404.4700

Waltzing of a Helium Pair in Tungsten: Migration Barrier and Trajectory Revealed from First-Principles

J. G. Niu·Q. Zhan·W. T. Geng
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Abstract

Despite well documented first-principles theoretical determination of the low migration energy (0.06 eV) of a single He in tungsten, fully quantum mechanical calculations on the migration of a He pair still present a challenge due to the complexity of its trajectory. By identifying the six most stable configurations of the He pair in W and decomposing its motion into rotational, translational, and rotational-translational routines, we are able to determine its migration barrier and trajectory. Our density functional theory calculations demonstrate a He pair has three modes of motion: a close or open circular two-dimensional motion in (100) plane with an energy barrier of 0.30 eV, a snaking motion along [001] direction with a barrier of 0.30 eV, and a twisted-ladder motion along [010] direction with the two He swinging in the plane (100) and a barrier of 0.31 eV. The graceful associative movements of a He pair are related to the chemical-bonding-like He-He interaction being much stronger than its migration barrier in W. The excellent agreement with available experimental measurements (0.24-0.32 eV) on He migration makes our first-principles result a solid input to obtain accurate He-W interatomic potentials in molecular dynamics simulations.

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J. G. Niu, Q. Zhan, W. T. Geng. 2014-04-18. Waltzing of a Helium Pair in Tungsten: Migration Barrier and Trajectory Revealed from First-Principles. https://arxiv.org/abs/1404.4700

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