Li 2 Fe SiO 4 has potential to be used as the next generation large - scale Li - battery. While its structure is still under controversy: it has been reported an orthorhombic structure by one group, and another group reported a monoclinic structure . In this paper, the first - principle calculation results show that the total energies of the orthorhombic structure and monoclinic structure are so close to each other, which implies the two structures should exist at the same time. Th e most interesting point is that Li 2 Fe SiO 4 maybe exists as a more complicated structure in which the orientation of FeO 4 - SiO 4 tetrahedron is randomly arranged upwards or downwards.