[Pw_forum] Ecutwfc question

[Alan J. R. Ambrozio]

I Have a simple question about relaxation. I'm working with a supercell of
216 atoms, an amorphous (carbon + hydrogen) material. The obtained results
for energy were as follows:

Ecut(Ry)   Total Energy    Total Energy/atom     Total force Ry/A
   40      -2350.90316498    -10.88381094              0.087283
   60      -2353.20485284    -10.89446691              0.076404
   80      -2353.33194348    -10.89505529              0.077286
  100      -2353.41150563    -10.89542363              0.077982
  120      -2353.42860197    -10.89550278              0.078147
  140      -2353.43026886    -10.89551050              0.078132
  160      -2353.43072890    -10.89551263              0.078139
  180      -2353.43180533    -10.89551761              0.078163
  200      -2353.43250424    -10.89552085              0.078150


I'd like to perform NMR calculations using GIPAW,  could someone help me,
 what is the best  ecutwf to use (accuracy + computational time)?  I'm
using these pseudopotentials
  C.pbe-tm-gipaw.UPF
  H.pbe-tm-gipaw.UPF

Thank very much.





-- 
Alan J. R. Ambrozio
Visitant PhD student
Room E19-722
Massachusetts Institute of Technology
857 316-8562
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