@article{18557,
  abstract     = {{We describe the software package SPEX, which allows first-principles calculations of quasiparticle and collective electronic excitations in solids using techniques from many-body perturbation theory. The implementation is based on the full-potential linearized augmented-plane-wave (FLAPW) method, which treats core and valence electrons on an equal footing and can be applied to a wide range of materials, including transition metals and rare earths. After a discussion of essential features that contribute to the high numerical efficiency of the code, we present illustrative results for quasiparticle band structures calculated within the GW approximation for the electronic self-energy, electron-energy-loss spectra with inter- and intraband transitions as well as local-field effects, and spin-wave spectra of itinerant ferromagnets. In all cases the inclusion of many-body correlation terms leads to very good quantitative agreement with experimental spectroscopies.}},
  author       = {{Schindlmayr, Arno and Friedrich, Christoph and Şaşıoğlu, Ersoy and Blügel, Stefan}},
  issn         = {{2196-7156}},
  journal      = {{Zeitschrift für Physikalische Chemie}},
  number       = {{3-4}},
  pages        = {{357--368}},
  publisher    = {{Oldenbourg}},
  title        = {{{First-principles calculation of electronic excitations in solids with SPEX}}},
  doi          = {{10.1524/zpch.2010.6110}},
  volume       = {{224}},
  year         = {{2010}},
}

@article{18632,
  abstract     = {{We present measurements of the effective electron mass in biaxial tensile strained silicon on insulator (SSOI) material with 1.2 GPa stress and in unstrained SOI. Hall-bar metal oxide semiconductor field effect transistors on 60 nm SSOI and SOI were fabricated and Shubnikov–de Haas oscillations in the temperature range of T=0.4–4 K for magnetic fields of B=0–10 T were measured. The effective electron mass in SSOI and SOI samples was determined as mt=(0.20±0.01)m0. This result is in excellent agreement with first-principles calculations of the
effective electron mass in the presence of strain.}},
  author       = {{Feste, Sebastian F. and Schäpers, Thomas and Buca, Dan and Zhao, Qing Tai and Knoch, Joachim and Bouhassoune, Mohammed and Schindlmayr, Arno and Mantl, Siegfried}},
  issn         = {{1077-3118}},
  journal      = {{Applied Physics Letters}},
  number       = {{18}},
  publisher    = {{American Institute of Physics}},
  title        = {{{Measurement of effective electron mass in biaxial tensile strained silicon on insulator}}},
  doi          = {{10.1063/1.3254330}},
  volume       = {{95}},
  year         = {{2009}},
}

@inproceedings{18634,
  abstract     = {{A computational method to obtain optical conductivities from first principles is presented. It exploits a relation between the conductivity and the complex dielectric function, which is constructed from the full electronic band structure within the random-phase approximation. In contrast to the Drude model, no empirical parameters are used. As interband transitions as well as local-field effects are properly included, the calculated spectra are valid over a wide frequency range. As an illustration I present quantitative results for selected simple metals, noble metals, and ferromagnetic transition metals. The implementation is based on the full-potential linearized augmented-plane-wave method.}},
  author       = {{Schindlmayr, Arno}},
  booktitle    = {{Theoretical and Computational Nanophotonics: Proceedings of the 2nd International Workshop}},
  editor       = {{Chigrin, Dmitry N.}},
  isbn         = {{978-0-7354-0715-2}},
  issn         = {{1551-7616}},
  location     = {{Bad Honnef}},
  number       = {{1}},
  pages        = {{157--159}},
  publisher    = {{American Institute of Physics}},
  title        = {{{Optical conductivity of metals from first principles}}},
  doi          = {{10.1063/1.3253897}},
  volume       = {{1176}},
  year         = {{2009}},
}

@article{18636,
  abstract     = {{We derive formulas for the Coulomb matrix within the full-potential linearized augmented-plane-wave (FLAPW) method. The Coulomb matrix is a central ingredient in implementations of many-body perturbation theory, such as the Hartree–Fock and GW approximations for the electronic self-energy or the random-phase approximation for the dielectric function. It is represented in the mixed product basis, which combines numerical muffin-tin functions and interstitial plane waves constructed from products of FLAPW basis functions. The interstitial plane waves are here expanded with the Rayleigh formula. The resulting algorithm is very efficient in terms of both computational cost and accuracy and is superior to an implementation with the Fourier transform of the step function. In order to allow an analytic treatment of the divergence at k=0 in reciprocal space, we expand the Coulomb matrix analytically around this point without resorting to a projection onto plane waves. Without additional approximations, we then apply a basis transformation that diagonalizes the Coulomb matrix and confines the divergence to a single eigenvalue. At the same time, response matrices like the dielectric function separate into head, wings, and body with the same mathematical properties as in a plane-wave basis. As an illustration we apply the formulas to electron-energy-loss spectra (EELS) for nickel at different k vectors including k=0. The convergence of the spectra towards the result at k=0 is clearly seen. Our all-electron treatment also allows to include transitions from 3s and 3p core states in the EELS spectrum that give rise to a shallow peak at high energies and lead to good agreement with experiment.}},
  author       = {{Friedrich, Christoph and Schindlmayr, Arno and Blügel, Stefan}},
  issn         = {{0010-4655}},
  journal      = {{Computer Physics Communications}},
  number       = {{3}},
  pages        = {{347--359}},
  publisher    = {{Elsevier}},
  title        = {{{Efficient calculation of the Coulomb matrix and its expansion around k=0 within the FLAPW method}}},
  doi          = {{10.1016/j.cpc.2008.10.009}},
  volume       = {{180}},
  year         = {{2009}},
}

@article{18564,
  abstract     = {{In the context of photoelectron spectroscopy, the GW approach has developed into the method of choice for computing excitation spectra of weakly correlated bulk systems and their surfaces. To employ the established computational schemes that have been developed for three-dimensional crystals, two-dimensional systems are typically treated in the repeated-slab approach. In this work we critically examine this approach and identify three important aspects for which the treatment of long-range screening in two dimensions differs from the bulk: (1) anisotropy of the macroscopic screening, (2) k-point sampling parallel to the surface, (3) periodic repetition and slab-slab interaction. For prototypical semiconductor (silicon) and ionic (NaCl) thin films we quantify the individual contributions of points (1) to (3) and develop robust and efficient correction schemes derived from the classic theory of dielectric screening.}},
  author       = {{Freysoldt, Christoph and Eggert, Philipp and Rinke, Patrick and Schindlmayr, Arno and Scheffler, Matthias}},
  issn         = {{1550-235X}},
  journal      = {{Physical Review B}},
  number       = {{23}},
  publisher    = {{American Physical Society}},
  title        = {{{Screening in two dimensions: GW calculations for surfaces and thin films using the repeated-slab approach}}},
  doi          = {{10.1103/PhysRevB.77.235428}},
  volume       = {{77}},
  year         = {{2008}},
}