First-principles study on thermal neutron cross sections of electron-doped lithium hydride

LiH is designated as a promising moderator and shielding material because of its low density, high melting point and large fraction of H atoms. Previous work was done to produce full and partial phonon spectra of LiH in a primitive cell and then be used to generate thermal neutron scattering cross sections of H in LiH and Li in LiH using the NJOY code system. A re-evaluate work with super cells was done in this paper to modify DFT (Density Function Theory) calculations' error in First Principles^[1]. The overall agreement of the lattice constants for pure LiH with the experiments is excellent if the zero-point motion is taken into account. From the theoretical calculation for electron (n)-doped LiH, it is indicated that metallic n-doped LiH was found to be a good superconductor ^[2]. The phonon spectrum was predicted to be significantly softened, with both Li and H vibrations softened with the introduction of the dopant. Analysis was done in this paper to study thermal neutron scattering cross sections of this electron (n)-doped LiH. A comparison of the generated cross sections shows that accounting for the dopant introduced in the calculations affects the cross sections mainly in some energy range, and the phonon effect mainly occurs at low temperature, which is helpful to study the neutronic properties of LiH, especially for the reactors used LiH moderator.