Atomistic properties of helium in hcp titanium: A first-principles study

First-Principles Study of the Structural Stability and Electronic and Elastic Properties of Helium inα-Zirconium

“…It is much smaller than BO , which means that He atoms can be trapped easily by preexisting vacancies. This is consistent with the case of Ti [2]. For materials used in nuclear systems, energetic particles like neutrons, ions, or electrons can induce significant microstructure alteration, especially the generation of large concentrations of vacancies, which can strongly affect the He distribution.…”

“…It is also important for the understanding of such effects as damage trapping, bubble nucleation, embrittlement, and blistering [6]. It has been found that, in different metals, He atoms preferentially occupy different sites: substitutional sites for Fe, Cr, Mo, and W [6,43], tetrahedral sites for Er [34], and FC (the center of equilateral trigonal face shared by two adjacent octahedrons) sites for Ti [2]. To identify the lowest energy configurations of the He interstitial defects in Zr and the possible influences of He concentration, supercells with 35 to 54 Zr atoms and one He atom were studied.…”

“…Helium has been a topic of sustained interest during the past several decades for both nuclear material engineering and fundamental research. In particular, numerous experimental and theoretical studies have been dedicated to addressing the properties of He in metals such as Ti [1,2], Fe [3,4], and W [5,6]. It is known to affect the nucleation and growth of voids in metals, causing noticeable dimensional changes and significant hardening [7][8][9][10].…”

The effect of helium nano-bubbles on the structures stability and electronic properties of palladium tritides: a density functional theory study

“…The formation energy per helium atom is decreasing as the number of helium atoms increases, indicating that a helium atom in an octahedral site can attract more helium atoms and form a cluster of at least up to six helium atoms, as calculated here. The He 2 forms a pair in the octahedral site with a He-He distance of 1.73 Å, which is very close to the value of 1.704 Å in the hcp Ti structure [16]. For He 3 , the most stable structure formed is a scalene triangle in the octahedral site with He-He distances of 1.87, 1.88 and 1.886 Å.…”

“…Helium binding energies for the PdT 0.22 system are very close to a number of metals, e.g. 0.65 eV for Pd, 0.66 eV for Ti and 0.43 eV for Fe [4,14,16]. The helium binding energy in nickel, on the other hand, is found to be near constant at about 2 eV for He 6 and large clusters [30] and in an fcc Pd lattice, a value of 1.33 eV was found for a He 4 cluster [14].…”