First-principles Hartree-Fock description of the electronic structure of monoclinic C2/m LixMnO2 (1 ≥ x ≥ 0)

First-principles periodic spin-unrestricted Hartree-Fock calculations of C2/m and Pnmn LiMnO2 are reported which indicate that the ground-state valence configuration is essentially d5 with a local moment close to 4μB in an antiferromagnetic (AF3) spin arrangement. Calculations for unrelaxed 25% periodic Li-Mn antisite disordered C2/m and Pnmm structures are entirely consistent with a value of about 10% disorder reported for the C2/m phase. For the system LixMnO2 in the region 1 ≤ x ≤ ½, where the C2/m structure is apparently retained and the discharge voltage associated with Li removal is constant, Mulliken analyses and spin-density distributions indicate that the valence configuration of Mn is essentially unaltered with the formation of localized holes on the 0 sites with strong spin polaron character as in MnO. Both the Fermi and the LI removal energies are calculated to change by only a few per cent. In this region, new empty O(p) states are created below the conduction-band edge of LiMnO2, fr...