[QE-developers] An unsolvable bug when using EPW

[mermaidyy]

Dear Quantum ESPRESSO Developers：
I have recently encountered an unsolvable bug while calculating superconductivity for a certain material system using EPW. The settings in my ‘nscf.in’ file are:
nscf.in
&control
  calculation = 'bands',
  prefix = 'NbMgB4',
  pseudo_dir = '../',
  outdir = './',
  wf_collect = .true.,
  verbosity='high'
 /
 &system    
  ibrav = 0,
  nat = 6,
  ntyp = 3,
  ecutwfc = 65,
  ecutrho = 600.0,
  smearing = 'mp',
  occupations = 'smearing',
  !nosym = .true.,
  !noinv = .true.,
  degauss = 0.05
/
&electrons 
  diagonalization = 'david',
  mixing_mode = 'plain',
  mixing_beta = 0.3,
  conv_thr = 1.0d-8
 /
 ATOMIC_SPECIES
 Mg 24.305 Mg.pbesol-n-kjpaw_psl.0.3.0.UPF
 Nb 92.91 Nb.pbesol-spn-kjpaw_psl.0.3.0.UPF
 B 10.811 b_pbesol_v1.4.uspp.F.UPF


CELL_PARAMETERS {bohr}
  5.7979 0.00000 0.00000
  0.00000 10.146 0.00000
  0.00000 0.00000 6.3104


 ATOMIC_POSITIONS crystal
Mg -0.0000000000000000 0.0000000000000000 -0.0000000000000000
Nb 0.5000000000000000 0.5000000000000000 -0.0000000000000000
B -0.0000000000000000 0.3322622395511202 0.5000000000000000
B 0.5000000000000000 0.8331863993084528 0.5000000000000000
B -0.0000000000000000 0.6677377894488785 0.5000000000000000
B 0.5000000000000000 0.1668135716915483 0.5000000000000000


K_POINTS crystal
216
  0.00000000 0.00000000 0.00000000 4.629630e-03
  0.00000000 0.00000000 0.16666667 4.629630e-03
  0.00000000 0.00000000 0.33333333 4.629630e-03
  ......
  0.83333333 0.83333333 0.50000000 4.629630e-03
  0.83333333 0.83333333 0.66666667 4.629630e-03
  0.83333333 0.83333333 0.83333333 4.629630e-03 (which were generated using ‘kmesh.pl’ 6×6×6)


For the phonon calculation, my ‘ph.in’ file is:
&inputph
  prefix='NbMgB4',
  fildyn='NbMgB4.dyn.xml',
  fildvscf='dvscf',
  tr2_ph=1.0d-10,
  ldisp=.true.,
  nq1 = 3,
  nq2 = 3,
  nq3 = 3,
 /
And some relevant parameters in my ‘epw.in’ file are:
mp_mesh_k = .true.
use_ws = .true.
  nk1 = 6
  nk2 = 6
  nk3 = 6
  nq1 = 3
  nq2 = 3
  nq3 = 3
  nkf1 = 12
  nkf2 = 12
  nkf3 = 12
  nqf1 = 6
  nqf2 = 6
  nqf3 = 6
/
After submitting the epw job, I get the error: Error in routine createkmap (1): is this a uniform k-mesh?
Then I set ‘’nosym = .true.‘’ in the ‘nscf.in’ file. then I get:
= BAD TERMINATION OF ONE OF YOUR APPLICATION PROCESSES
= RANK 0 PID 6279 RUNNING AT d111
= KILLED BY SIGNAL: 6 (Aborted)
After that, I removed ‘’nosym=.true.‘’ from  ‘nscf.in’ , but EPW again reports the ‘’is this a uniform k-mesh?‘’ error. If I instead use ‘’K_POINTS automatic‘’ in  nscf.in’  as：
K_POINTS automatic
6 6 6 0 0 0
then the error becomes: inconsistent nscf and elph k-grids
other methods such as：
1.K_POINTS automatic
6 6 6 1 1 1
2.Modify the grid density of k-points and q-points.
3.Comment out this line：mp_mesh_k = .true.
are unable to solve the problem.
No matter what I try, these errors persist. Could you please help me analyze the cause? Thank you very much for your attention!
Yours 
             Yandong Yang 



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