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Free keywords:
Many-body perturbation theory; GW approach; LAPW method; Quasi-particles
Abstract:
The GW method has become the state-of-the-art approach for the first-principles description of
the electronic quasi-particle band structure in crystalline solids. Most of the existing codes rely on
pseudopotentials in which only valence electrons are treated explicitly. The pseudopotential method
can be problematic for systems with localized d- or f -electrons, even for ground-state density-functional
theory (DFT) calculations. The situation can become more severe in GW calculations, because pseudowavefunctions
are used in the computation of the self-energy and the core–valence interaction is
approximated at the DFT level. In this work, we present the package FHI-gap, an all-electron GW
implementation based on the full-potential linearized augmented planewave plus local orbital (LAPW)
method. The FHI-gap code can handle core, semicore, and valence states on the same footing,
which allows for a correct treatment of core–valence interaction. Moreover, it does not rely on any
pseudopotential or frozen-core approximation. It is, therefore, able to handle a wide range of materials,
irrespective of their composition. Test calculations demonstrate the convergence behavior of the results
with respect to various cut-off parameters. These include the size of the basis set that is used to expand
the products of Kohn–Sham wavefunctions, the number of k points for the Brillouin zone integration, the
number of frequency points for the integration over the imaginary axis, and the number of unoccupied
states. At present, FHI-gap is linked to the WIEN2k code, and an implementation into the exciting code
is in progress.
