[Pw_forum] problem in optimizing nanotubes in QE
lorenzo.paulatto at impmc.upmc.fr
Wed Sep 16 09:25:20 CEST 2015
On Wednesday, September 16, 2015 08:46:32 AM Naiwrit Karmodak wrote:
> This is a 3,3 nanotube. I have also tried with 6,6 nanotube and the problem
> is same. Both david and cg option for diagonalization is not giving any way
> to optimized geometry. Please suggest a solution for this.
changing the type of diagonalization (cg or david) can affect the convergence
of a single scf step, but the structure optimization will not change.
If your structure breaks down it is because it is not stable, at least with
the functional you are using. Visualizing your input with xcrysden I can see
that all your carbon atoms are stuck together, which means that your input is
wrong. My guess is that you wanted to specify the atoms positions as fractions
of the crystall lattice vectors, in this case you have to use the "crystal"
C 0.0863 0.1169 0.0443
C 0.9137 0.8831 0.132
Also note that specifying a k-point shift along the x and y directions is not
correct, because you want wavefunctions which are periodic over the unit cell
in those directions. I.e. use
1 1 10 0 0 1
Finally, please disregards the advice from Bahadir, especially the one about
smearing, as reducing smearing will not necessarily make convergence easier.
HTH, kind regards
Dr. Lorenzo Paulatto
IdR @ IMPMC -- CNRS & Université Paris 6
+33 (0)1 44 275 084 / skype: paulatz
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4 place Jussieu 75252 Paris Cédex 05
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