# Input File Description ## Program: turbo_spectrum.x / turboTDDFPT / Quantum Espresso (version: 6.4)
> > ### TABLE OF CONTENTS INTRODUCTION &lr_input prefix | outdir | verbosity | itermax0 | itermax | extrapolation | epsil | units | start | end | increment | ipol | eels | td | eign_file ### INTRODUCTION
> >         Input data format: { } = optional, [ ] = it depends.

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

> >     BEWARE: TABS, DOS <CR><LF> CHARACTERS ARE POTENTIAL SOURCES OF TROUBLE

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

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

> >     &lr_input
> >       ...
> >     /
## Namelist: &lr_input
This namelist is always needed !
prefix | CHARACTER
Default: | 'pwscf'
>     Sets the prefix for generated and read files. The files
>     generated by the ground state pw.x run should have this
>     same prefix.
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outdir | CHARACTER
Default: | './'
>     The directory that contains the run critical files, which
>     include the files generated by ground state pw.x run.
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verbosity | INTEGER
Default: | 1
>     This integer variable controls the amount of information
>     written to standard output.
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itermax0 | INTEGER
Default: | 500
>     Number of Lanczos coefficients to be read from the file.
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itermax | INTEGER
Default: | 500
>     The total number of Lanczos coefficients that will be
>     considered in the calculation of the polarizability/absorption
>     coefficient. If itermax > itermax0, the Lanczos coefficients
>     in between itermax0+1 and itermax will be extrapolated.
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extrapolation | CHARACTER
Default: | 'no'
>         Sets the extrapolation scheme. 'osc'= biconstant extrapolation,
>     'constant'=constant extrapolation and 'no'=no extrapolation.
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epsil | REAL
Default: | 0.02
>     The broadening/damping term (in Rydberg units).
[Back to Top]
units | INTEGER
Default: | 0
>         The unit system used for the output and the start, end and increment
>     input parameters.

>     0 = Rydbergs, 1 = Electron volts and 2 = Nanometres per electron volts.
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start | REAL
Default: | 0.0
>       The polarizability and the absorption coefficient are computed
>     starting from this value. In units set by the units variable.
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end | REAL
Default: | 2.5
>       The polarizability and the absorption coefficient are computed
>     up to this value. In units set by the units variable.
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increment | REAL
Default: | 0.001
>       Incremental step used to define the mesh between start and end.
>     In units set by the units variable.
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ipol | INTEGER
Default: | 1
>     An integer variable that determines which element of the
>     dynamical polarizability will be computed:
>     1 -> alpha_xx(omega), 2 -> alpha_yy(omega), and
>     3 -> alpha_zz(omega). When set to 4, three Lanczos chains
>     are sequentially performed and the full polarizability
>     tensor and the absorption coefficient are computed.
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eels | LOGICAL
Default: | .false.
>     Must be set to .true. for EELS. EELS-specific operations
>     will be performed.
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td | CHARACTER
Default: | 'lanczos'
>     When set to 'lanczos', a calculation of the spectrum is
>     performed using the Lanczos coefficients.
>     When set to 'davidson' or 'david', a calculation of the
>     spectrum is performed using the eigenvalues computed
>     using the Davidson algorithm. See the variable 'eign_file'.
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eign_file | CHARACTER
Default: | 'pwscf.eigen'
>     The name of the file produced by the turbo_davidson.x code,
>     in which are written the eigenvalues.
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This file has been created by helpdoc utility on Fri Mar 01 17:57:33 CET 2019.