Pressure dependence of dynamically screened Coulomb interactions in NiO: Effective Hubbard, Hund, intershell, and intersite components

In this work, we report the pressure dependence of the effective Coulomb interaction parameters (Hubbard U) in paramagnetic NiO within the constrained random phase approximation (cRPA). We consider five different low-energy models starting from the most expensive one that treats both Ni-d and O-p states as correlated orbitals (dp-dp model) to the smallest possible two-orbital model comprising the eg states only (eg-eg model). We find that in all the considered models, the bare interactions are not very sensitive to the compression. However, the partially screened interaction parameters show an almost linear increment as a function of compression, resulting from the substantial weakening of screening effects upon compression. This counterintuitive trend is explained from the specific characteristic changes of the basic electronic structure of this system. We further calculate the nearest-neighbor intersite d-d interaction terms, which also show substantial enhancement due to compression. The computed interaction parameters for antiferromagnetic NiO are almost identical to their paramagnetic counterparts. Results for other prototypical 3d transition metal monoxides, FeO, CoO, and CuO, further demonstrate that the monotonic increase of the partially screened interaction parameters under the application of pressure is a generic characteristic of transition metal monoxides. Finally, the effective parameters of 3d states grow as a function of the atomic number of the transition metal ion.