Importance of electronic correlations in exploring the exotic phase diagram of layered Li_xMnO₂

Using ab initio dynamical mean-field theory we explore the electronic and magnetic states of layered Li_xMnO₂ as a function of x, the state-of-charge. Constructing real-space Wannier projections of Kohn-Sham orbitals based on the low-energy subspace of Mn 3d states and solving a multi-impurity problem, our approach focuses on local correlations at Mn sites. The antiferromagnetic insulating state in LiMnO₂ has a moderate Néel temperature of T_N = 296K in agreement with experimental studies. Upon delithiation the system proceeds through a number of states: ferrimagnetic correlated metals at x = 0.92, 0.83; multiple charge disproportionated ferromagnetic correlated metals with large quasiparticle peaks at x = 0.67, 0.50, 0.33; ferromagnetic metals with small quasiparticle peaks at x = 0.17, 0.08 and an antiferromagnetic insulator for the fully delithiated state, x = 0.0. At moderate states of charge, x = 0.67-0.33, a mix of +3/+4 formal oxidation states of Mn is observed, while the overall nominal oxidation of Mn state changes from +3 in LiMnO₂ to +4 in MnO₂. In all these cases the high-spin state emerges as the most likely state in our calculations considering the full d manifold of Mn based on the proximity of e_g levels in energy to t_2g. We observe a crossover from coherent to incoherent behavior on delithiation as function of state-of-charge.