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<input_description distribution="Quantum Espresso" package="turboTDDFPT" program="turbo_lanczos.x" >
   <toc>
   </toc>
   <intro>
    Input data format: { } = optional, [ ] = it depends.

All quantities whose dimensions are not explicitly specified are in
RYDBERG ATOMIC UNITS

BEWARE: TABS, DOS &lt;CR&gt;&lt;LF&gt; CHARACTERS ARE POTENTIAL SOURCES OF TROUBLE

Comment lines in namelists can be introduced by a &quot;!&quot;, exactly as in
fortran code. Comments lines in ``cards&apos;&apos; can be introduced by
either a &quot;!&quot; or a &quot;#&quot; character in the first position of a line.

Structure of the input data:
===============================================================================

&amp;lr_input
  ...
/

&amp;lr_control
  ...
/

[ &amp;lr_post
  ...
 / ]
   </intro>
   <namelist name="lr_input" >
      <label> This namelist is always needed !
      </label>
      <var name="prefix" type="CHARACTER" >
         <default> &apos;pwscf&apos;
         </default>
         <info>
Sets the prefix for generated and read files. The files
generated by the ground state pw.x run should have this
same prefix.
         </info>
      </var>
      <var name="outdir" type="CHARACTER" >
         <default> &apos;./&apos;
         </default>
         <info>
The directory that contains the run critical files, which
include the files generated by ground state pw.x run.
         </info>
      </var>
      <var name="wfcdir" type="CHARACTER" >
         <default> &apos;./&apos;
         </default>
         <info>
The directory that contains the run critical files, which
include the files generated by ground state pw.x run.
         </info>
      </var>
      <var name="restart" type="LOGICAL" >
         <default> .false.
         </default>
         <info>
When set to .true., turbo_lanczos.x will attempt to restart
from a previous interrupted calculation. (see <ref>restart_step</ref>
variable).

Beware, if set to .false. turbo_lanczos.x will OVERWRITE any
previous runs.
         </info>
      </var>
      <var name="restart_step" type="INTEGER" >
         <default> itermax
         </default>
         <info>
The code writes restart files every restart_step iterations.
Restart files are automatically written at the end of
itermax Lanczos steps.
         </info>
      </var>
      <var name="lr_verbosity" type="INTEGER" >
         <default> 1
         </default>
         <info>
This integer variable controls the amount of information
written to standard output.
         </info>
      </var>
      <var name="disk_io" type="CHARACTER" >
         <default> &apos;default&apos;
         </default>
         <info>
    Fine control of disk usage. Currently only &apos;reduced&apos; is
supported where no restart files are written, apart from
the &apos;default&apos; mode.
         </info>
      </var>
   </namelist>
   <namelist name="lr_control" >
      <var name="itermax" type="INTEGER" >
         <default> 500
         </default>
         <info>
Number of Lanczos iterations to be performed.
         </info>
      </var>
      <var name="ipol" type="INTEGER" >
         <default> 1
         </default>
         <info>
An integer variable that determines which element of the
dynamical polarizability will be computed:
1 -&gt; alpha_xx(omega), 2 -&gt; alpha_yy(omega), and
3 -&gt; alpha_zz(omega). When set to 4, three Lanczos chains
are sequentially performed and the full polarizability
tensor and the absorption coefficient are computed.
         </info>
      </var>
      <var name="n_ipol" type="INTEGER" >
         <default>
    1 if ipol &lt; 4;
3 if ipol=4
         </default>
         <info>
    Determines the number of zeta coefficients to be calculated
for a given polarization direction.
         </info>
      </var>
      <var name="ltammd" type="LOGICAL" >
         <default> .false.
         </default>
         <info>
When set to .true. the Tamm-Dancoff approximation is used
in constructing the Liouvillian.
         </info>
      </var>
      <var name="no_hxc" type="LOGICAL" >
         <default> .false.
         </default>
         <info>
When set to .true. the change in the internal field
(Hartree and exchange-correlation) is ignored in the
calculation, resulting in the independent electron
approximation.
         </info>
      </var>
      <var name="lrpa" type="LOGICAL" >
         <default> .false.
         </default>
         <info>
When set to .true. the Random Phase Approximation
is used (no exchange and correlation).
         </info>
      </var>
      <var name="scissor" type="REAL" >
         <default> 0.0
         </default>
         <info>
Scissor shift (in Rydberg units).
         </info>
      </var>
      <var name="charge_response" type="INTEGER" >
         <default> 0
         </default>
         <info>
When set to 1, the code computes the response of the charge
density and writes it into a file format determined by the
variable plot type. Setting charge response to 1 makes the
presence of the card lr post mandatory.
         </info>
      </var>
      <var name="pseudo_hermitian" type="LOGICAL" >
         <default> .true.
         </default>
         <info>
When set to .true. the pseudo-Hermitian Lanczos
algorithm is used. When set to .false. the
non-Hermitian Lanczos biorthogonalization algorithm
is used (which is two times slower).
         </info>
      </var>
      <var name="d0psi_rs" type="LOGICAL" >
         <default> .false.
         </default>
         <info>
When set to .true. the dipole is computed in the
real space. When set to .false. the dipole is
computed in the reciprocal space by computing [H,r].
Note, currently the commutator does not contain
a contribution for hybrids [V_EXX,r]. See also
the variable lshift_d0psi.
Important: Treatment of the dipole in the real space
is allowed only if the system is finite.
         </info>
      </var>
      <var name="lshift_d0psi" type="LOGICAL" >
         <default> .true.
         </default>
         <info>
This variable is used only when <ref>d0psi_rs</ref> = .true.
a) If a molecule is placed in the corner of the
supercell, there is a discontinuity problem for the
position operator r, which is not periodic. By setting
lshift_d0psi=.true. the discontinuity problem is
solved by shifting the position operator r such that
it is continuous and well defined.
b) If a molecule is placed in the center of the supercell,
there is no discontinuity problem for the position operator r,
and thus you can set lshift_d0psi=.false. But if you still
set it to .true., this will not harm, because the position
operator will basically remain as it is, since it is always
centered wrt the center of the molecule.
         </info>
      </var>
   </namelist>
   <namelist name="lr_post" >
      <var name="omeg" type="REAL" >
         <default> 0.0
         </default>
         <info>
    The response of the charge density is calculated for this
transition energy (in Rydberg units)
         </info>
      </var>
      <var name="epsil" type="REAL" >
         <default> 0.02
         </default>
         <info>
The broadening/damping term (in Rydberg units).
         </info>
      </var>
      <var name="beta_gamma_z_prefix" type="CHARACTER" >
         <default> &apos;pwscf&apos;
         </default>
         <info>
The prefix of the file where the beta gamma zeta coefficients
from the first calculation can be set manually using this
parameter. The file outdir/beta gamma z prefix.beta gamma z.x
(where x=1-3) must exist.
         </info>
      </var>
      <var name="w_T_npol" type="INTEGER" >
         <default> 1
         </default>
         <info>
Number of polarization directions considered in the previous
calculation. It must be set to 3 if in the previous calculation
 ipol=4, it must be set to 1 otherwise.
         </info>
      </var>
      <var name="plot_type" type="INTEGER" >
         <default> 1
         </default>
         <info>
    An integer variable that determines the format of the file
containing the charge density response. 1: A file containing
the x y z grid coordinates and the corre- sponding value of
the density is produced 2: The density response is written
in Xcrysden format 3: The density response is written in
the gaussian cube format.
         </info>
      </var>
   </namelist>
</input_description>