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

Lithium silicates, such as Li2SiO3 and Li4SiO4, 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 Li2SiO3 and Li4SiO4 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 Li2SiO3 exhibit significantly different electron distributions. The Si 3s and 3p hybridization is observed in Li2SiO3, but not in Li4SiO4. The mechanical elastic constants reflected Li4SiO4 might be unstable in some degrees.