First principal investigation of Fe- and Li- silicon compounds

Electronic and geometric structure of β-phase crystal FeSi2 as well as β-FeSi2 nanofilms and Si/FeSi2 interface is investigated by DFT calculations. It is revealed unusual increasing of the dielectric gap of crystal FeSi2 under different pressures. It is detected that (001) surface of β-FeSi2 slab, ended by Si atoms, is reconstructed with squares formed by Si atoms. Also FeSi2 nanofilms have conductivity explained by Fe atom layers. It is shown that contact of the (001) Si and β-FeSi2 plate lead to narrow perfect interface having conductivity near Fermi level mainly due to contribution of the silicide surface lavers. Also properties of lithium absorption inside crystal and amorphous silicon as well as inside silicon with impurities were investigated. For that a new method was developed which allow calculating a diffusion rate inside amorphous material when potential barriers are too high to apply conventional molecular dynamic method. It is demonstrated strong increasing of the lithium diffusion rate inside amorphous silicon in comparison with crystal silicon.