Why this code

This code has been conceived with the purpose of enabling GW-BSE calculations in large model structures, as for such systems sums over empty states become a serious issue we devised a method to eliminate them completely from the calculation. Note that the main GW-BSE codes support Gamma-only sampling and work with norm-conserving pseudopotentials.
The package contains also the SIMPLE codes which support k-points sampling albeit preservig sums over empty orbitals.

Main features GW

  • G0W0 approximation
  • Basis for polarizability operators: G vectors or optimal basis sets
  • No sums over empty states
  • Treatment of isolated and extended systems
  • Analytic continuation approach
  • collinear spin polarization
  • NEW: full-linear response formulation without storing W
  • NEW: fast and approximate e-ph coupling

Main features BSE

  • Tamm-Dancoff approximation
  • No sums over empty orbitals
  • W can be calculated on-the-fly through linear response
  • Treatment of isolated and extended systems
  • Calculation of complex dielectric function through Lanczos algorithm
  • Calculation of excited states
  • Real-Space Real-Time TD-BSE
  • collinear spin polarization
  • NEW: fast and approximate e-ph coupling

Main features SIMPLE

  • RPA and BSE calculation of optical spectra
  • collinear spin or full-relativistic SOC
  • Use of reduced Shirley's bases for KS orbitals and for their products

Main features not released yet or under development

  • Contour integration
  • off-diagonal self-energy terms
  • approximate treatment of semicore states
  • partially occupied states

These programs are distributed in the hope that they will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.