Electronic Properties of NiO at Ultrahigh Pressure

https://doi.org/10.1134/S106377612109003X

The effect of the high pressure on the electronic properties of NiO is studied within the multielectron approach. The low energy physics is described by the effective Hubbard model based on Ni d-electrons and O p-electrons in three charge sectors of the Hilbert space: neutral states (configurations d8 + d9L + d10L2), electron removal states (configurations d7 + d8L + d9L2), and electron addition states (d9 + d10L) with L denotes a ligand hole. Due to a high spin (HS)-low spin (LS) crossover in the electron removal states at pressure PS determined by a competition of the intraatomic Hund exchange interaction and increasing with pressure crystal field 10Dq, the effective Hubbard parameter Ueff and the insulator gap Eg depend on pressure. We find weak increasing of Eg for P < PS and weak decreasing Eg for P > PS. The Mott-Hubbard transition pressure is estimated to be in the interval 450–650 GPa.