GW approximation with LSDA+U method and applications to NiO, MnO, and V$_2$O$_3$

Nonadiabatic Atomic-like State Stabilizing Antiferromagnetism and Mott Insulation in MnO

In this paper I report evidence that the antiferromagnetic and insulating ground state of MnO is caused by a nonadiabatic atomic-like motion as it is evidently the case in NiO. In addition, I show that the experimental findings of Goodwin et al. [Phys. Rev. Lett. (2006), 96,~047209] corroborate my suggestion that the rhombohedral-like distortion in antiferromagnetic MnO as well as in antiferromagnetic NiO is an inner distortion of the monoclinic base-centered Bravais lattice of the antiferromagnetic phases.

压力依赖的电子相互作用与磁序对 MnO 和 NiO 中压力驱动绝缘体-金属转变的重要性

Importance of pressure-dependent electronic interactions and magnetic order on pressure-driven insulator-metal transitions in MnO and NiO

本研究基于 doubly-screened Coulomb correction 方法，探讨了压力依赖的电子相互作用与磁序对 MnO 和 NiO 绝缘体-金属转变的影响，发现混合泛函能更准确描述高压性质，并揭示了 NiO 反铁磁态在压力下的失稳现象。

Pressure-driven magnetic moment collapse in the ground state of MnO

The zero temperature Mott transition region in antiferromagnetic, spin S=5/2 MnO is probed using the correlated band theory LSDA+U method. The first transition encountered is an insulator-insulator volume collapse within the rocksalt structure that is characterized by an unexpected Hund's rule violating `spin-flip' moment collapse. This spin-flip to S=1/2 takes fullest advantage of the anisotropy of the Coulomb repulsion, allowing gain in the kinetic energy (which increases with decreasing volume) while retaining a sizable amount of the magnetic exchange energy. While transition pressures vary…

Ab-Initio self-energy embedding for the photoemission spectra of NiO and MnO

The accurate ab-initio simulation of periodic solids with strong correlations is one of the grand challenges of condensed matter. While mature methods exist for weakly correlated solids, the ab-initio description of strongly correlated systems is an active field of research. In this work, we show results for the single particle spectral function of the two correlated $d$-electron solids NiO and MnO from self-energy embedding theory. Unlike earlier work, the theory does not use any adjustable parameters and is fully ab-initio, while being able to treat both the strong correlation and the non-lo…

Correlation effects in the ground state charge density of Mott-insulating NiO: a comparison of ab-initio calculations and high-energy electron diffraction measurements

Accurate high-energy electron diffraction measurements of structure factors of NiO have been carried out to investigate how strong correlations in the Ni 3d shell affect electron charge density in the interior area of nickel ions and whether the new ab-initio approaches to the electronic structure of strongly correlated metal oxides are in accord with experimental observations. The generalized gradient approximation (GGA) and the local spin density approximation corrected by the Hubbard U term (LSDA+U) are found to provide the closest match to experimental measurements. The comparison of calcu…

Ab initio calculation of resonant X-ray scattering in Manganites

We study the origin of the resonant x-ray signal in manganites and generalize the resonant cross-section to the band structure framework. With {\it ab initio} LSDA and LSDA+U calculations we determine the resonant x-ray spectrum of LaMnO$_3$. The calculated spectrum and azimuthal angle dependence at the Mn $K$-edge reproduce the measured data without adjustable parameters. The intensity of this signal is directly related to the orthorhombicity of the lattice. We also predict a resonant x-ray signal at the La $L$-edge, caused by the tilting of the MnO$_6$ octahedra. This shows that the resonant…

关于 NiO 和 MnO 的磁结构与晶体结构

On Magnetic and Crystal Structures of NiO and MnO

本文利用高分辨率中子衍射和各向同性子群表示方法分析了 NiO 和 MnO 的磁与晶体结构，确定最佳解为 1k-单斜模型，磁空间群为 C_c2/c。

GW+U real-space Green's function calculations of x-ray spectra

The Hubbard model is implemented in real-space Green's function calculations of x-ray spectra using an effective self-energy adapted from the LSDA+U method of Anisimov et al. This self-energy consists of an energy-dependent many-pole approximation to the GW self-energy with an additive correction due to on-site Coulomb repulsion among the partially filled localized-electron states. This leads to a GW+U approach which provides an efficient procedure to account for local correlation effects on x-ray spectra. Results are presented for the spin and angular momentum projected density of states of M…

Electronic structure of bulk manganese oxide and nickel oxide from coupled cluster theory

We describe the ground- and excited-state electronic structure of bulk MnO and NiO, two prototypical correlated electron materials, using coupled cluster theory with single and double excitations (CCSD). As a corollary, this work also reports the first implementation of unrestricted periodic ab initio equation-of motion CCSD. Starting from a Hartree-Fock reference, we find fundamental gaps of 3.46 eV and 4.83 eV for MnO and NiO respectively for the 16 unit supercell, slightly overestimated compared to experiment, although finite-size scaling suggests that the gap is more severely overestimated…

Metal-ligand interplay in strongly-correlated oxides: a parametrized phase diagram for pressure induced spin transitions

We investigate the magnetic properties of archetypal transition-metal oxides MnO, FeO, CoO and NiO under very high pressure by x-ray emission spectroscopy at the Kβline. We observe a strong modification of the magnetism in the megabar range in all the samples except NiO. The results are analyzed within a multiplet approach including charge-transfer effects. The pressure dependence of the emission line is well accounted for by changes of the ligand field acting on the d electrons and allows us to extract parameters like local d-hybridization strength, O-2p bandwidth and ionic crystal field acro…