  We calculate the density of states (DOS) and the Mulliken population of the
diamond and the co-doped diamonds with different concentrations of lithium (Li)
and phosphorus (P) by the method of the density functional theory, and analyze
the bonding situations of the Li-P co-doped diamond thin films and the impacts
of the Li-P co-doping on the diamond conductivities. The results show that the
Li-P atoms can promote the split of the diamond energy band near the Fermi
level, and improve the electron conductivities of the Li-P co-doped diamond
thin films, or even make the Li-P co-doped diamond from semiconductor to
conductor. The effect of Li-P co-doping concentration on the orbital charge
distributions, bond lengths and bond populations is analyzed. The Li atom may
promote the split of the energy band near the Fermi level as well as may
favorably regulate the diamond lattice distortion and expansion caused by the P
atom.
