# List of input variables

## Error message

Deprecated function: The each() function is deprecated. This message will be suppressed on further calls in node_privacy_byrole_nodeapi_prepare() (line 216 of /var/www/exc/sites/all/modules/node_privacy_byrole/node_privacy_byrole.module).

 !----- Type of calculation (default: linear response:tddft) ------------------- linear ! default: linear response in G space. ! solving the tddft equation for \chi ! this is not implemented in EXC

exciton ! excitonic calculation (the EXC code) in transition space
!--------------------------------------------------------------------------------

!---------- Energies for the diagonal part of H^exc (default:enks) ---------------------------------
enks ! default: use the Kohn-Sham eigenvalues found in the ground-state file
! to construct the diagonal of H^exc
gw ! perturbative GW energies: this variable implies the existence of a gwfile
qpsenergy ! self-consistent quasiparticle energies. this variable implies the
! existence of a qps file
so ! scissor operator correction.
! see below soenergy, stretch_valence, stretch_conduction
soenergy ! value of the scissor correction. default: 0.0
stretch_valence ! stretch = GW bandwidth / DFT bandwidth. default: 1.0
stretch_conduction ! modify energy in a linear way in order to reproduce the GW bandwidth
! like: e_GW = e_DFT * stretch
somult ! multi-scissor operator correction. implies the existence of a file
! called somult.in
!---------------------------------------------------------------------------------------------------

!---------- Wavefunctions for the matrix elements (default:kss) ----------------------------
kss ! default. use the Kohn-Sham wavefunctions found in the ground-state file
! to construct the numerator of \chi^0
qps ! self-consistent quasiparticle eavefunctions. this variable implies the existence
! of a qps file
!-------------------------------------------------------------------------------------------

!------ Tamm-Dancoff Approximation (default) ---------------------------------------------------------
tammdancoff ! if this flag occurs the calculation will use the so-called Tamm-Dancoff approximation,
! i.e. only the resonant part of H^exc will be taken into account
resonant ! equivalent to tammdancoff
!-----------------------------------------------------------------------------------------------------

!--- Exciton solver (default:fulldiago) --------------------------------------------------------------
fulldiago ! default. diagonalization of the excitonic hamiltonian.
haydock ! iterative inversion of the excitonic hamiltonian. implies the variable niter (see below).
! only the final spectrum is obtained but no excitonic eigenvalues and eigenvectors,
! preventing further analysis.
niter ! number of iterations for the haydock iterative procedure. default:100
haydock_restart ! write restart file. default false
!-----------------------------------------------------------------------------------------------------

!---- Screening --------------------------------------------------------------------------
wdiag ! default: only the diagonal (in G) of Wgg' is retained. it turns out to be a good
! approximation for solids
wfull !the whole gg' structure of W is used. important for clusters.

lf ! default: calculate also the exchange term >.
nlf ! avoid the calculation of the exchange term >. if rpa this corresponds to
! to a calculation without local fields.
!------------------------------------------------------------------------------------------

!----- Use of shikted k-points --------------------------------------------------
shiftk ! if the ground state structure has been calculated using shifted
! k-points, we have to tell dp about it, otherwise it will try to use
! the symmetries of the system to sample the whole Brillouin zone.
! Alternatively (and deprecatively) you can still use the old way ...
nsymk 1 ! force EXC to consider only the first symmetry (the identity)
noinvk ! do not use inversion
! Remember: either one uses the 'shiftk' flag OR 'nsym 1' + 'noinv'
!--------------------------------------------------------------------------------

!----- convergency parameters ----------------------------------------------------
npwwfn ! number of plane waves to describe the wavefunctions
! default: all plane waves found on the _KSS file will be used
wfnsh ! number of shells of plane waves to describe the wavefunctions
! default:all
! Remark: only one of the above parameters has to be specified

npwmat ! number of G-vectors for the \epsilon matrix (related to local
! fields) ! default:all
matsh ! number of shells og G-vectors for the \epsilon matrix (related
! to local fields) ! default:all
! Remark: only one of the above parameters has to be specified

nbands ! number of the last band (highest energy) to be included in the
! calculation ! default:all
lomo ! number of the first band (lowest energy) to be included in the
! calculation ! default:1
!---------------------------------------------------------------------------------

!-- Pseudopotential --------------------------------------------------------------
novkb ! exclude the nonlocal part of the pseudopotential, which is unfortunately
! the leading term for a big number of transitions
!---------------------------------------------------------------------------------

!----- Momentum Transfer - Polarization of light ---------------------------------
q
! This specifies the momentun transfer (vector) to the
! system. The value of q can range from 0 to very high
! value (several Brilloun zones equivalent)
! Very high q vector can be found in Electron energy loss
! or Inelastic X-ray Scattering. The case q=0 is
! particularly important for optical absorption, where the
! polarization of light can be secified giving a small
! value in one or another direction, e.g.
! q 0.0001 0.0001 0.0
! Remark: q uses the reduced coordinates here, not the
! cartesian ones.
doublegrid ! Allows to read two separate KSS-files for initial and final
! states, which are shifted by q with respect to each other.
! (e.g. k.p perturbation theory will be avoided at small q)
! USAGE: dp -i -k -k
! dp1.kss corresponds to the final states at k,
! dp2.kss corresponds to the initial states at k-q
antieps ! calculation of eps*(-q,-w) instead of eps(q,w), which
! corresponds to exchanging the two kss files in doublegrid
!---------------------------------------------------------------------------------

!----- Other flags -----------------------------------------------------------------
savememory ! if present this flag will make the code calculating the rhotw
! at any transition with a double Fourier transform, rather than
! storing the wave functions in real space. Advantage: reduction