Crystalline and electronic structures of lithium silicates: A density functional theory study

Abstract

Lithium silicates, such as Li 2SiO 3 and Li 4SiO 4, are considered as favorable candidates for the tritium breeding materials of a deuterium–tritium type nuclear fusion reactor. Their bulk structural and electronic properties are investigated using pseudopotential plane wave (PPW) method within density functional theory (DFT). The optimized crystal structure parameters are well consistent with the experimental results. The results indicate that Li 2SiO 3 and Li 4SiO 4 are insulators with band gaps of about 5.36 and 5.53 eV, respectively. The valence electrons density of state reveal the covalency properties mainly resulting from the overlapping of O 2p and Si 3p orbital electrons in both lithium silicates. The nonbridging O (NBO) atoms and bridging O (BO) atoms of Li 2SiO 3 exhibit significantly different electron distributions. The Si 3s and 3p hybridization is observed in Li 2SiO 3, but not in Li 4SiO 4. The mechanical elastic constants reflected Li 4SiO 4 might be unstable in some degrees.