EPW Forum

Posted: **Fri Jul 31, 2026 1:53 pm**

Dear all,

I am encountering the following error during the second EPW run (explrn = .true.) of an exciton-polaron calculation using Quantum ESPRESSO 7.5 (EPW). I am following the LiF exciton-polaron tutorial for all the previous steps. The first EPW run completes successfully and writes the Wannier Hamiltonian.

epw2.out:

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    -------------------------------------------------------------------
     Using SnS2.ukk from disk
     -------------------------------------------------------------------

     HDF5 is used in the current build. Exciton-phonon coupling calculations are enabled.
     Symmetries of Bravais lattice:  24
     Symmetries of crystal:          12

     Do not need to read .epb files; read .fmt files


     Band disentanglement is used: nbndsub =    9

     Computes the analytic long-range interaction for polar materials [lpolar]
      
     Use zone-centred Wigner-Seitz cells 
     Number of WS vectors for electrons        0
     Number of WS vectors for phonons        0
     Number of WS vectors for electron-phonon        0
     Maximum number of cores for efficient parallelization        0
     Results may improve by using use_ws == .TRUE. 

     Reading Hamiltonian, Dynamical matrix and EP vertex in Wann rep from file


     Finished reading Wann rep data from file

     ===================================================================
     Memory usage:  VmHWM =       303Mb
                   VmPeak =       579Mb
     ===================================================================
     
     Using q-mesh file: ./path.kpt
     Size of q point mesh for interpolation:        301
     Using k-mesh file: ./path.kpt
     Size of k point mesh for interpolation:        301
     Max number of k points per pool:                4

 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
     Error in routine cdiagh2 (8):
     info =/= 0
 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

I am also attaching the inputs of epw1.in and epw2.in

epw1.in:

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&inputepw

! General Flags 
  prefix      = 'AB'
  outdir      = './'
  dvscf_dir   = './save/'

! Core EPW Control Flags 
  elph        = .true. 
  epwwrite    = .true.
  epwread     = .false.
  epbwrite    = .true.
  epbread     = .false.
  etf_mem     = 0
  epw_memdist = .true.


! Wannierization Flags
  wannierize   = .true.
  eig_read     = .true.

  nbndsub      = 9
  num_iter     = 20000

  iprint       = 2

  proj(1)      = 'A : p'
  proj(2)      = 'B : p'
  
  dis_win_max  = xyz
  dis_froz_max = xyz
  dis_froz_min = xyz
  dis_win_min  = xyz

  wdata(1)     = 'bands_plot = .true.'
  wdata(2)     = 'begin kpoint_path'
  wdata(3)     = 'G 0.0000 0.0000 0.0000 M 0.5000 0.0000 0.0000'
  wdata(4)     = 'M 0.5000 0.0000 0.0000 K 0.3333 0.3333 0.0000'
  wdata(5)     = 'K 0.3333 0.3333 0.0000 G 0.0000 0.0000 0.0000'
  wdata(6)     = 'end kpoint_path'
  wdata(7)     = 'bands_plot_format = gnuplot xmgrace'
  wdata(8)     = 'guiding_centres = .true.'
  wdata(9)     = 'dis_num_iter      = 10000'
  wdata(10)    = 'dis_conv_window  = 10'
  wdata(11)    = 'dis_conv_tol     = 1.0e-9'
  wdata(12)    = 'conv_window  = 10'
  wdata(13)    = 'conv_tol     = 1.0e-9'



! Real-Space Visualization of W90 functions
  wdata(14)    = 'wannier_plot = .true.'
  wdata(15)    = 'wannier_plot_supercell = 4 4 2'
  wdata(16)    = 'wannier_plot_radius = 3.5'


! Exciton-Polaron Flags
  lpolar                 = .true. 
  exciton                = .true.
  explrn                 = .false.

! No. of exciton states
  negnv_explrn = 20 
  nbndv_explrn = 13   ! Match the valence band in BSE calcs. 
  nbndc_explrn = 13   ! Match the conduction band in BSE calcs.  


! Brillouin Zone (BZ) Grid Flags (Coarse Grids)
  nk1 = 10
  nk2 = 10
  nk3 = 1 
  nq1 = 10
  nq2 = 10
  nq3 = 1
  
  asr_typ = 'crystal'
  use_ws  = .true.  
  lifc    = .false.


! Plotting Band Structure and Phonons
  band_plot              = .true.
  filkf                  = './path.kpt'
  filqf                  = './path.kpt'
  
/

epw2.in:

Code: Select all

inputepw

! General Flags 
  prefix                 = 'AB'
  outdir                 = './'
  dvscf_dir              = './save/'

! Core EPW Control Flags  
  elph         = .true.
  epbwrite     = .false.
  epbread      = .false.
  epwwrite     = .false.
  epwread      = .true.
  etf_mem      = 0

! Wannier Basis Flags  
  wannierize   = .false.
  nbndsub      = 9


! Exciton-Polaron Flags
  lpolar       = .true.  
  exciton      = .true.
  explrn       = .true.

  negnv_explrn = 20 
  nbndv_explrn = 13   ! Match the valence band in BSE calcs. 
  nbndc_explrn = 13   ! Match the conduction band in BSE calcs. 

  init_plrn    = 5
  niter_plrn   = 500

  band_plot              = .true.
  filkf                  = './path.kpt'
  filqf                  = './path.kpt'
  
/

EPW Forum

Error in routine cdiagh2 (8): info =/= 0 (exciton-polaron calculation)

Error in routine cdiagh2 (8): info =/= 0 (exciton-polaron calculation)