Sternheimer

Name HamiltonianVariation
Section Linear Response::Sternheimer
Type integer
Default hartree+fxc

The terms to be considered in the variation of the Hamiltonian. The external potential (V_ext) is always considered. The default is to include also the exchange-correlation and Hartree terms, which fully takes into account local fields. Just hartree gives you the random-phase approximation (RPA). If you want to choose the exchange-correlation kernel, use the variable XCKernel. For kdotp and magnetic em_resp modes, or if TheoryLevel = independent_particles, the value V_ext_only is used and this variable is ignored.

Options:

• V_ext_only:
  Neither Hartree nor XC potentials included.
  
• hartree:
  The variation of the Hartree potential only.
  
• fxc:
  The exchange-correlation kernel (the variation of the exchange-correlation potential) only.
  

Name PhotonEta
Section Linear Response::Sternheimer
Type float
Default 0.0000367

This variable provides the value for the broadening of the photonic spectra when the coupling of electrons to photons is enabled in the frequency-dependent Sternheimer equation

Name Preorthogonalization
Section Linear Response::Sternheimer
Type logical

Whether initial linear-response wavefunctions should be orthogonalized or not against the occupied states, at the start of each SCF cycle. Default is true only if SmearingFunction = semiconducting, or if the Occupations block specifies all full or empty states, and we are not solving for linear response in the occupied subspace too.