First-principles study of helium clustering at initial stage in ThO ₂

Abstract

The clustering behavior of helium atoms in thorium dioxide has been investigated by first-principles calculations. The results show that He atoms tend to form a cluster around an octahedral interstitial site (OIS). As the concentration of He atoms in ThO 2 increases, the strain induced by the He atoms increases and the octahedral interstitial site is not large enough to accommodate a large cluster, such as a He hexamer. We considered three different Schottky defect (SD) configurations (SD 1 , SD 2 , and SD 3 ). When He atoms are located in the SD sites, the strain induced by the He atoms is released and the incorporation and binding energies decrease. The He trimer is the most stable cluster in SD 1 . Large He clusters, such as a He hexamer, are also stable in the SDs.

First principles study on lattice vibration and electrical properties of layered perovskite Sr2 M 2O7 (M = Nb, Ta)

“…With the development of computers, the theoretical researches of materials have increased, especially based on the first principles. [13][14][15] Nisar et al, [16] based on hybrid functionals (HSE06), surveyed the photocatalytic of Sr 2 Nb 2 O 7 from the band structure and bandgap. The results showed that the band gap in layered perovskite Sr 2 Nb 2 O 7 was significantly reduced by the cationic-anionic co-doping, and band position was excellent for the visible-light photocatalysis.…”