The electronic structure, lattice dynamics, and electron–phonon coupling (EPC) of electron (n)-doped LiH have been extensively studied using ab initio methods within the virtual crystal approximation. The overall agreement of the lattice constants and bulk modulus for pure LiH with the experiments is excellent if the zero-point motion is taken into account. From the theoretical calculation for n-doped LiH, it is indicated that metallic n-doped LiH might be a good superconductor. Moreover, the EPC parameter λ for n-doped LiH was found to increase with the dopant concentration, resulting from the softening of optical phonon modes and the increase of the electron density of states at the Fermi level, while a decreasing trend of λ was predicted for the presence of pressure. Phonon linewidth calculations suggested that the optical phonon mode makes the main contribution to the EPC. A possible mechanism for the predicted superconductivity of n-doped LiH has been discussed.

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Helium (He) is a typical impurity element and plays a crucial role in the microstructural evolution in nuclear materials under irradiation. Here, we systematically investigate the interactions between He and self-interstitial atoms (SIAs) as well as their influences on the kinetic behaviors of SIAs in tungsten (W), using both first-principles and object kinetic Monte Carlo methods. It is found that there are attractive interactions between He and SIAs, which become stronger with the increasing of SIA numbers. Specifically, the He-SIA1 and He-SIA2 complexes adopt a three-dimensional (3D) migration pattern with an effective energy barrier of 0.38 and 0.61 eV, respectively, which is completely different from the 1D migration of SIAs in W (⩽0.033 eV) without He. Such an unexpected collaborative 3D motion of He-SIA complexes increases the probability of vacancy-interstitial recombination and reduces the number of surviving defects. Consequently, our calculations reveal the enhanced effect of He on the self-healing efficiency in W, which is originated from the collaborative 3D motion of He-SIA complexes. The current results can improve our fundamental understanding of the influence of He on the evolution of irradiation defects and have great implications to estimate the performance of W-PFMs in fusion environment.

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