First-principles investigation of charge disproportionation in HoNiO＿3 perovskite

We have investigated the electronic structure of HoNiO_3 perovskit e using first principles based on the density_functional theory. A comparison of elec tron_density map between orthorhombic and monoclinic structures indicated that there is only one type of Ni^3+state in the orthorhombic_metallic phase (space group Pbnm), and there are two types of Ni^(3-δ)+ and Ni^(3+δ) + states in the monoclinic_insulating phase ( space group P2_1/n). The characteristic parameter of charge di sproportionation δis concerned with the non_bonding t_2g band of partial density of states of Ni3d electron. δis calculated to be 0. 34±0.01， based on the changes of t_2gband from orthorhombic to monoclinic phase.