Waltzing of a helium pair in tungsten: Migration barrier and trajectory revealed from first-principles

• Published in: AIP advances Vol. 4; no. 6; pp. 067128 - 067128-8
• Main Authors: Niu, J. G., Zhan, Q., Geng, W. T.
• Format: Journal Article
• Language: English
• Published: Melville American Institute of Physics 01.06.2014; AIP Publishing LLC
• Subjects: Barriers; Bonding strength; CHEMICAL BONDS; DENSITY FUNCTIONAL METHOD; Density functional theory; EV RANGE; First principles; HELIUM; INTERACTIONS; MATERIALS SCIENCE; Mathematical analysis; MIGRATION; Molecular dynamics; MOLECULAR DYNAMICS METHOD; Organic chemistry; QUANTUM MECHANICS; SIMULATION; SOLIDS; Three dimensional motion; Trajectories; TUNGSTEN
• ISSN: 2158-3226; 2158-3226
• DOI: 10.1063/1.4884304

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.