New development beyond the GW approximation and its application to the electronic structure of solids

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1. Takada has calculated the quasiparticle energy of the electron liquid, based on his own theory that enables one to consider by iteration all Feynman diagrams for the self-energy by requiring the Pauli principle in the framework of the conserving approximation method. He has then obtained the same conclusion by Yasuhara et al (1999) that the narrowing in the occupied bandwidth of simple metals predicted from angular resolved photoemission experiments is in fact ascribed to the traditional use of the free electron energy as the final state level and on the contrary the bandwidth is somewhat increased under the influence of exchange and correlation if one uses the quasiparticle energy instead. His calculation has for the first time allowed for an inseparable coupling of one-pair (or plasmon) and multi-pair excitations. 2. Using the same theory Takada has also calculated the dynamical structure factor S(q,ω) of the electron liquid over the entire region of metallic densities and found t … More hat the ω-linear spectral shape due to one-pair excitations at low ω is enhanced by particlehole multiple scattering and the destructive interference between one and multi-pair excitations produces a flauened spectral structure at intermediate ω. These are quite different from the conventional RPA spectral shape. 3. Using the Yasuhara-Takada theory (1991) Ishihara et al have performed a band calculation of sodium and found that its occupied bandwidth is by less than 10% increased under the influence of exchange and correlation. They have ascertained that the Fermi surface distortion of sodium from the perfect sphere is determined by the pseudo-potential, not influenced by exchange and correlation between conduction electrons. 4. Yasuhara and Higuchi have constructed an orbital-dependent correlation energy functional for use in band calculations in combination with the orbital-dependent exchange energy functional, borrowing the knowledge of long-, intermediate-, and short-range correlations from the electron liquid. They have predicted that heavy fermion systems probably will be interpreted in terms of the correlation-induced reconstruction of Kohn-Sham orbitals in the vicinity of the Fermi level where the density of states is extraordiarily enhaced by mixing conduction and f-electron orbitals to gain the magnitude of that orbital-dependent correlation energy functional. Less