[Pw_forum] Learning TDDFT calculation in Atomic label (CH4 molecule) using turbo_lanczos.x and turbo_davidson.x

[prem sen]

Dear Dr. Iurii Timrov,
                             Thanks again for your valuable reply.
I knew, how to check the convergence using both the codes but to cross
verify myself, I asked you the question. Now I get the same absorption
spectra for CH4 molecule using both the code (turbo_lanczos.x &
turbo_davidson.x).

I was also trying for Carbon-dimer. But I am facing a basic problem.
Without using, occupations = "smearing", this system is not getting
converged. If I use "smearing", turbo_davidson.x or turbo_lanczs.x is not
possible. I have tried with different kinds of PPs, "mixing_mode" and
"mixing_beta". Is there any solution for this problem ??

For Example I have used ::

&CONTROL
  calculation  = "scf",
  restart_mode = "from_scratch"
  prefix       = "C2",
  pseudo_dir   = "../pseudo/",
  outdir       = "./tmp/",
/
&SYSTEM
  ibrav     = 0,
!  celldm(1) = 20,
  nat       = 2,
  ntyp      = 1,
  ecutwfc   = 25,
  ecutrho   = 250,
  nosym     = .true.,
!  occupations = "smearing",
!  smearing  = "mv",
!  degauss   = 0.001,
/
&ELECTRONS
  diagonalization='david'
  mixing_mode = 'plain'
  mixing_beta = 0.6,
  conv_thr =  1.0d-8
/
CELL_PARAMETERS angstrom
15.0  0.0  0.0
 0.0 15.0  0.0
 0.0  0.0 15.0
ATOMIC_SPECIES
C  12.01  C.pbe-rrkjus.UPF
ATOMIC_POSITIONS (angstrom)
C        1.255833278   0.000000000   0.000000000
C        0.000000000   0.000000000   0.000000000
K_POINTS {Gamma}


Thanks & regards,
Prem Sen
Ph.D. Student,
IIT Bombay,
Mumbai,India.
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