Takao Kotani

Quasiparticle self-consistent GW theory.

In past decades the scientific community has been looking for a reliable first-principles method to predict the electronic structure of solids with high accuracy. Here we present an approach which we call the quasiparticle self-consistent approximation. It is based on a kind of self-consistent perturbation theory, where the self-consistency is constructed to minimize the perturbation. We apply it to selections from different classes of materials, including alkali metals, semiconductors, wide band gap insulators, transition metals, transition metal oxides, magnetic insulators, and rare earth compounds. Apart from some mild exceptions, the properties are very well described, particularly in weakly correlated cases. Self-consistency dramatically improves agreement with experiment, and is sometimes essential. Discrepancies with experiment are systematic, and can be explained in terms of approximations made.

All-Electron Self-Consistent GW Approximation: Application to Si, MnO, and NiO

We present a new kind of self-consistent GW approximation based on the all-electron, full-potential linear muffin-tin orbital method. By iterating the eigenfunctions of the GW Hamiltonian, self-consistency in both the charge density and the quasiparticle spectrum is achieved. We explain why this form of self-consistency should be preferred to the conventional one. Some results for Si (a representative semiconductor) are presented. Finally we consider many details in the electronic structure of the antiferromagnetic insulators MnO and NiO. Excellent agreement with experiment is shown for many properties, suggesting that a Landau quasiparticle (energy band) picture provides a reasonable description of electronic structure even in these correlated materials.

All-electron GW calculation based on the LAPW method: Application to wurtzite ZnO

We present a new, all-electron implementation of the GW approximation and apply it to wurtzite ZnO. Eigenfunctions computed in the local-density approximation (LDA) by the full-potential linearized augmented-plane-wave (LAPW) or the linearized muffin-tin-orbital (LMTO) method supply the input for generating the Green function G and the screened Coulomb interaction W. A mixed basis is used for the expansion of W, consisting of plane waves in the interstitial region and augmented-wavefunction products in the augmentation-sphere regions. The frequency-dependence of the dielectric function is computed within the random-phase approximation (RPA), without a plasmon-pole approximation. The Zn 3d orbitals are treated as valence states within the LDA; both core and valence states are included in the self-energy calculation. The calculated bandgap is smaller than experiment by about 1eV, in contrast to previously reported GW results. Self-energy corrections are orbital-dependent, and push down the deep O 2s and Zn 3d levels by about 1eV relative to the LDA. The d level shifts closer to experiment but the size of shift is underestimated, suggesting that the RPA overscreens localized states.

Quasiparticle self-consistent GW method : A basis for the independent-particle approximation

We have developed a type of self-consistent scheme within the

All-electron GW approximation with the mixed basis expansion based on the full-potential LMTO method

GW

Adequacy of approximations in GW theory

approximation, which we call quasiparticle self-consistent

Ab Initio Prediction of Conduction Band Spin Splitting in Zinc Blende Semiconductors

GW

An optimized-effective-potential method for solids with exact exchange and random-phase approximation correlation

(QS

Effects of alloying and strain on the magnetic properties of Fe 16 N 2

GW

Quasiparticle Self-Consistent GW Method Based on the Augmented Plane-Wave and Muffin-Tin Orbital Method

). We have shown that QS