FIRST-PRINCIPLES HARTREE-FOCK DESCRIPTION OF THE ELECTRONIC-STRUCTUREOF MONOCLINIC C2 M LIXMNO2 ER-THAN-OR-EQUAL-TO-X-GREATER-THAN-OR-EQUAL-TO-0)/

First-principles periodic spin-unrestricted Hartree-Fock calculations of C2/m and Pnmn LiMnO2 are reported which indicate that the ground-st ate valence configuration is essentially d(5) with a local moment clos e to 4 mu(B) in an antiferromagnetic (AF(3)) spin arrangement. Calcula tions for unrelaxed 25% periodic Li-Mn antisite disordered C2/m and Pn mn structures are entirely consistent with a value of about 10% disord er reported for the C2/m phase. Far the system LixMnO2 in the region 1 less than or equal to x less than or equal to 1/2, where the C2/m str ucture is apparently retained and the discharge voltage associated wit h Li removal is constant, Mulliken analyses and spin-density distribut ions indicate that the valence configuration of Mn is essentially unal tered with the formation of localized holes on the O sites with strong spin polaron character as in MnO. Both the Fermi and the Li removal e nergies are calculated to change by only a few per cent. In this regio n, new empty O(p) states are created below the conduction-band edge of LiMnO2, from which a bandgap of similar to 1.9 eV can be deduced, as in the case of NiO and MnO. No significant changes are found in the em pty Mn(d) states. It is suggested that the changes in the densities of unoccupied states, which are an accurate indicator of the nature of t he valence electron configurations,. should be directly verifiable by O K-edge spectroscopy and indirectly from the absence of any significa nt changes in the Mn K-and L-edge spectra.