  The three-dimensional ternary LiFeO2 compound presents various unusual
essential properties. The main features are thoroughly explored by the density
functional and many-body perturbation theory. The concise physical/chemical
picture, the critical spin-polarizations and orbital hybridizations in the Li-O
and Fe-O bonds, are clearly examined through geometric optimization,
quasi-particle energy spectra, spin-polarized density of states, the spatial
charge densities, the spin-density distributions, and the strong optical
responses. The unusual optical transitions cover various frequency-dependent
absorption structures, and the most prominent plasmon modes are identified by
the dielectric functions, energy loss functions, reflectance spectra, and
absorption coefficients. Optical excitations are anisotropic and strongly
affected by excitonic effects. The close combinations of electronic, magnetic
and optical properties allow us to identify the significant spin-polarizations
and orbital hybridizations for each available excitation channel. The lithium
ferrite compound can be used for spintronic and photo-catalysis applications.
