------------------------------------------------------------------------
INPUT FILE DESCRIPTION

Program: ph.x / PWscf / Quantum Espresso
------------------------------------------------------------------------


Input data format: { } = optional, [ ] = it depends, # = comment

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

title_line

&INPUTPH
   ...
/

xq(1) xq(2) xq(3)
[ irrep(1) irrep(2) ... irrep(nrapp)   ]     # if "nrapp" was specified
[ atom(1)  atom(2)  ... atom(nat_todo) ]     # if "nat_todo" was specified



========================================================================
Line of input:

      title_ph
   
   
   DESCRIPTION OF ITEMS:
   
      +--------------------------------------------------------------------
      Variable:       title_ph
      
      Type:           CHARACTER
      Description:    Title of the job, i.e., a line that is reprinted on output.
      +--------------------------------------------------------------------
      
===End of line-of-input=================================================


========================================================================
NAMELIST: &INPUTPH

   +--------------------------------------------------------------------
   Variable:       amass(i), i=1,ntyp
   
   Type:           REAL
   Default:        0.0
   Description:    Atomic mass [amu] of each atomic type.
                   If not specified, masses are read from data file
   +--------------------------------------------------------------------
   
   +--------------------------------------------------------------------
   Variable:       outdir
   
   Type:           CHARACTER
   Default:        './'
   Description:    Scratch directory.
   +--------------------------------------------------------------------
   
   +--------------------------------------------------------------------
   Variable:       prefix
   
   Type:           CHARACTER
   Default:        'pwscf'
   Description:    Prepended to input/output filenames;  must be the same
                   used in the calculation of unperturbed system.
   +--------------------------------------------------------------------
   
   +--------------------------------------------------------------------
   Variable:       niter_ph
   
   Type:           INTEGER
   Default:        50
   Description:    Maximum number of iterations in a scf step.
   +--------------------------------------------------------------------
   
   +--------------------------------------------------------------------
   Variable:       tr2_ph
   
   Type:           REAL
   Description:    Threshold for selfconsistency.
   Default:        1e-10
   +--------------------------------------------------------------------
   
   +--------------------------------------------------------------------
   Variable:       alpha_mix(niter)
   
   Type:           REAL
   Default:        alpha_mix(1)=0.7
   Description:    Mixing factor (for each iteration) for updating the scf potential:
                   
                   vnew(in) = alpha_mix*vold(out) + (1-alpha_mix)*vold(in)
   +--------------------------------------------------------------------
   
   +--------------------------------------------------------------------
   Variable:       nmix_ph
   
   Type:           INTEGER
   Description:    Number of iterations used in potential mixing.
   Default:        4
   +--------------------------------------------------------------------
   
   +--------------------------------------------------------------------
   Variable:       iverbosity
   
   Type:           INTEGER
   Default:        0
   Description:    0 = short output
                   1 = verbose output
   +--------------------------------------------------------------------
   
   +--------------------------------------------------------------------
   Variable:       reduce_io
   
   Type:           LOGICAL
   Description:    Reduce I/O to the strict minimum.
   Default:        .false.
   +--------------------------------------------------------------------
   
   +--------------------------------------------------------------------
   Variable:       max_seconds
   
   Type:           REAL
   Description:    Maximum allowed run time before the job stops smoothly.
   Default:        1.d7
   +--------------------------------------------------------------------
   
   +--------------------------------------------------------------------
   Variable:       fildyn
   
   Type:           CHARACTER
   Description:    File where the dynamical matrix is written.
   Default:        'matdyn'
   +--------------------------------------------------------------------
   
   +--------------------------------------------------------------------
   Variable:       fildrho
   
   Type:           CHARACTER
   Description:    File where the charge density responses are written.
   Default:        ' '
   +--------------------------------------------------------------------
   
   +--------------------------------------------------------------------
   Variable:       fildvscf
   
   Type:           CHARACTER
   Description:    File where the the potential variation is written
                   (for later use in electron-phonon calculation).
   Default:        ' '
   +--------------------------------------------------------------------
   
   +--------------------------------------------------------------------
   Variable:       epsil
   
   Type:           LOGICAL
   Default:        .false.
   Description:    If .true. in a q=0 calculation for a non metal the
                   macroscopic dielectric constant of the system is
                   computed. Do not set epsil to .true. if you have a
                   metallic system or q/=0: the code will complain and stop
   +--------------------------------------------------------------------
   
   +--------------------------------------------------------------------
   Variable:       lrpa
   
   Type:           LOGICAL
   Description:    If .true. the dielectric constant is calculated at the
                   RPA level with DV_xc=0.
   Default:        .false.
   +--------------------------------------------------------------------
   
   +--------------------------------------------------------------------
   Variable:       lnoloc
   
   Type:           LOGICAL
   Description:    If .true. the dielectric constant is calculated without
                   local fields, i.e. by setting DV_H=0 and DV_xc=0.
   Default:        .false.
   +--------------------------------------------------------------------
   
   +--------------------------------------------------------------------
   Variable:       trans
   
   Type:           LOGICAL
   Description:    if .true. the phonons are computed
                   if trans .and. epsil effective charges are calculated
   Default:        .true.
   +--------------------------------------------------------------------
   
   +--------------------------------------------------------------------
   Variable:       lraman
   
   Type:           LOGICAL
   Default:        .false.
   Description:    if .true. calculate nonresonant Raman coefficients
                   using second-order response as in:
                   M. Lazzeri and F. Mauri, Phys. Rev. Lett. 90, 036401 (2003)
   +--------------------------------------------------------------------
   
   ///---
      OPTIONAL VARIABLES FOR RAMAN:
      
      +--------------------------------------------------------------------
      Variable:       eth_rps
      
      Type:           REAL
      Description:    threshold for calculation of  Pc R |psi>
      Default:        1.0d-9
      +--------------------------------------------------------------------
      
      +--------------------------------------------------------------------
      Variable:       eth_ns
      
      Type:           REAL
      Description:    threshold for non-scf wavefunction calculation
      Default:        1.0e-12
      +--------------------------------------------------------------------
      
      +--------------------------------------------------------------------
      Variable:       dek
      
      Type:           REAL
      Description:    delta_xk used for wavefunction derivation wrt k
      Default:        1.0e-3
      +--------------------------------------------------------------------
      
   \\\---
   
   +--------------------------------------------------------------------
   Variable:       recover
   
   Type:           LOGICAL
   Description:    if .true. restart from an interrupted run
   Default:        .false.
   +--------------------------------------------------------------------
   
   +--------------------------------------------------------------------
   Variable:       elph
   
   Type:           LOGICAL
   Default:        .false.
   Description:    if .true. electron-phonon lambda coeffs are computed
                   
                   For metals only, requires gaussian smearing.
                   
                   If elph .and. trans, the lambdas are calculated in the same
                   run, using the same k-point grid for phonons and lambdas
                   If elph.and..not.trans, the lambdas are calculated using
                   previously saved DeltaVscf in fildvscf, previously saved
                   dynamical matrix, and the present punch file. This allows
                   the use of a different (larger) k-point grid.
   +--------------------------------------------------------------------
   
   +--------------------------------------------------------------------
   Variable:       zue
   
   Type:           LOGICAL
   Description:    if .true. in a q=0 calculation for a non metal the
                   effective charges are computed from the phonon
                   density responses. Note that if trans.and.epsil
                   effective charges are calculated using a different
                   algorithm. The results should be the same within
                   numerical noise.
   +--------------------------------------------------------------------
   
   +--------------------------------------------------------------------
   Variable:       elop
   
   Type:           LOGICAL
   Default:        .false.
   Description:    if true calculate electro-optic tensor
   +--------------------------------------------------------------------
   
   +--------------------------------------------------------------------
   Variable:       fpol
   
   Type:           LOGICAL
   Default:        .false.
   Description:    if .true. calculate dynamic polarizabilities
                   ( experimantal stage, see example33 for calculation
                     of methane )
   +--------------------------------------------------------------------
   
   +--------------------------------------------------------------------
   Variable:       lnscf
   
   Type:           LOGICAL
   Description:    If .TRUE. the run makes first a nscf calculation.
   Default:        .false.
   +--------------------------------------------------------------------
   
   +--------------------------------------------------------------------
   Variable:       ldisp
   
   Type:           LOGICAL
   Default:        .false.
   Description:    If .TRUE. the run calculates phonons for a grid of
                   q-points specified by nq1, nq2, nq3  - for direct
                   calculation of the entire phonon dispersion.
                   The pw.x data file should not be produced using
                   "calculation='phonon'" in this case.
   +--------------------------------------------------------------------
   
   +--------------------------------------------------------------------
   Variables:      nq1, nq2, nq3
   
   Type:           INTEGER
   Default:        0
   Description:    Parameters of the Monkhorst-Pack grid (no offset) used
                   when ldisp=.true. Same meaning as for nk1, nk2, nk3
                   in the input of pw.x.
   +--------------------------------------------------------------------
   
   +--------------------------------------------------------------------
   Variables:      iq1, iq2, iq3
   
   Type:           INTEGER
   Description:    These go together with nq1, nq2, nq3 and allow to choose
                   just one point out of the Monkhorst-Pack grid with ldisp=.true.
                   Note the the actual point chosen is something like
                   (iq1-1)/nq1, (iq2-1)/nq2, (iq3-1)/nq3 (so, check the
                                                          output for what you get). Also make sure that PW left *.wfc
                   files behind (no 'phonon' is needed though).
   +--------------------------------------------------------------------
   
   +--------------------------------------------------------------------
   Variable:       nrapp
   
   Type:           INTEGER
   Default:        0, i.e. use all irreps
   Description:    Choose the subset of irreducible representations (irreps)
                   for which the linear response calculation is performed:
                   "nrapp" irreps, specified in input (see below) are used.
                   
                   IMPORTANT:
                      * nrapp must be <= 3*nat
                      * do not specify "nat_todo" together with "nrapp"
   +--------------------------------------------------------------------
   
   +--------------------------------------------------------------------
   Variable:       maxirr
   
   Type:           INTEGER
   Default:        0, i.e.  use all irreps
   Description:    Perform calculations only up to the first "maxirr" irreps.
                   
                   IMPORTANT:
                      * maxirr must be <= 3*nat
                      * do not specify "nat_todo" or "nrapp" together with "maxirr"
   +--------------------------------------------------------------------
   
   +--------------------------------------------------------------------
   Variable:       nat_todo
   
   Type:           INTEGER
   Default:        0, i.e. displace all atoms
   Description:    Choose the subset of atoms to be used in the linear response
                   calculation: "nat_todo" atoms, specified in input (see below)
                   are displaced.
                   
                   IMPORTANT:
                       * nat_todo <= nat
                       * do not specify "nrapp" together with "nat_todo"
   +--------------------------------------------------------------------
   
===END OF NAMELIST======================================================


///---
   ========================================================================
   Line of input:
   
         xq(1)  xq(2)  xq(3)
      
      
      DESCRIPTION OF ITEMS:
      
         +--------------------------------------------------------------------
         Variables:      xq(1)  xq(2)  xq(3)
         
         Type:           REAL
         Description:    The phonon wavevector; must be equal to the one used
                         in the non-selfconsistent calculation (not read if
                         ldisp is true).
         +--------------------------------------------------------------------
         
         
   ===End of line-of-input=================================================
   
   
\\\---

________________________________________________________________________
* IF nrapp was specified : 

   ========================================================================
   Line of input:
   
         irrep(1) irrep(2) ... irrep(nrapp)
      
      
      DESCRIPTION OF ITEMS:
      
         +--------------------------------------------------------------------
         Variables:      irrep(1) irrep(2) ... irrep(nrapp)
         
         Type:           INTEGER
         Description:    The list of indices of irreps used in the  calculation
                         if  "nrapp" is specified.
         +--------------------------------------------------------------------
         
         
   ===End of line-of-input=================================================
   
   
    
* ELSE IF nat_todo was specified : 

   ========================================================================
   Line of input:
   
         atom(1)  atom(2) ... atom(nat_todo)
      
      
      DESCRIPTION OF ITEMS:
      
         +--------------------------------------------------------------------
         Variables:      atom(1)  atom(2) ... atom(nat_todo)
         
         Type:           INTEGER
         Description:    Contains the list of indices of atoms used in the
                         calculation if "nat_todo" is specified.
         +--------------------------------------------------------------------
         
         
   ===End of line-of-input=================================================
   
   
    
ENDIF
________________________________________________________________________