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Understanding the effect of alloying elements on the retention and clustering behavior of Helium (He) in Aluminum (Al) is a great help to study the radiation damage process of Al-based nuclear structure materials under He irradiation. Based on the first-principles calculations, we investigated the influence of Gallium (Ga) dopant on the formation of He n and He n V clusters in Al and Al-0.9 at% Ga (Al-Ga) alloy. We found that Ga dopant could influence the formation and growth of He clusters. In addition, the presence of Ga reduces the binding energy of both He n and He n V clusters, resulting in He dissociation from the clusters more easily. Moreover, Ga could serve as a trapping center by reducing the charge density in its vicinity to induce He nucleation in Al-Ga alloy compared to that in pure Al. Furthermore, the binding energy of He to vacancy around Ga is weaker than that around Al, suggesting that Ga will decrease the trapping capability of vacancy to He. We thus propose that Ga plays a key role in He clustering behavior. Our results are significant to understand the effect of dopant on He bubbling behavior and the distribution of damages in Al-Ga alloy under He irradiation. [ABSTRACT FROM AUTHOR]

Spin-crossover combined with metal–insulator transition and superconductivity has been found in 2D transition-metal phosphorous trichalcogenides when tuning them by high pressure. Simulation of such intriguing spin-crossover behaviors is crucial to understanding the mechanism. The Hubbard U correction is widely used to describe the strong on-site Coulomb interaction in the d electrons of transition-metal compounds, while the U values are sensitive to the crystal field and spin state varying greatly with pressure. In this work, we show that taking MnPS3 as an example and based on a uniform parameter set, the hybrid functional calculations give a spin-crossover pressure of 35 GPa consistent with experimental observation (30 GPa), which is less than half of the existing reported value (63 GPa) using the Hubbard U correction. Notably, we find a spin-crossover induced transition from an antiferromagnetic semiconductor with monoclinic stacking-order to a ferromagnetic semiconductor with rhombohedral stacking-order, and the ferromagnetism originates from the partially occupied t2g orbitals. Different from previous understanding, the Mott metal–insulator transition of MnPS3 does not occur simultaneously with the spin-crossover but in a pressurized low-spin phase. [ABSTRACT FROM AUTHOR]

The high-pressure (HP) properties of TlFeSe 2 are investigated based on the first-principles calculations combined with structure-searching method. The low-pressure C 2/ m phase will transform into the orthorhombic Pnma phase at 2 GPa, with 8% volume collapse, the insulator-metal transition and the bicollinear antiferromagnetic-to-nonmagnetic spin-crossover. At pressure higher than 8 GPa, the HP C 2/ m phase will become the ground state. Both Pnma phase and HP C 2/ m phase are constituted by one-dimensional chains of edge-sharing FeSe 5 tetragonal pyramids. Pressuring decrease the Se-Se bond length giving rise to the transition from [Se 2 ] 3- to [Se 2 ] 2- . Negative charge transfer causes the Fe 2+ with ∼2  μ B magnetic moment at ambient pressure and the nonmagnetic Fe 1.5+ at higher pressure. The Fermi surfaces of HP phases are also discussed., (© 2021 IOP Publishing Ltd.)