[Pw_forum] problem in optimizing nanotubes in QE

[Naiwrit Karmodak]

Hi,
I was trying to relax a nanotube in quantum espresso. But during
optimization the structure is breaking down and unable to converge. I am
giving the input file
&CONTROL
                 calculation = 'relax' ,
                restart_mode = 'from_scratch' ,
                      outdir = './' ,
                  pseudo_dir = '/mnt/lustre/ipc2/ipcnwrit/upf_files' ,
                   verbosity = 'low' ,
                    forc_conv_thr = 1.0D-3
 /
 &SYSTEM
                       ibrav = 0,
                         nat = 12,
                        ntyp = 1,
                     ecutwfc = 35,
                     ecutrho = 270 ,
                      occupations = 'smearing'
                      smearing = 'gaussian',
                      degauss = 0.05
 /
 &ELECTRONS
                    conv_thr = 1.0D-6 ,
                 mixing_mode = 'plain' ,
             diagonalization = 'cg' ,
                mixing_beta = 0.55
 /
 &IONS
                ion_dynamics = 'bfgs' ,
/
CELL_PARAMETERS
14.0 0.0 0.0
0.0 14.0 0.0
0.0 0.0 2.47
ATOMIC_SPECIES
    C   12.01000   C.pbe-rrkjus.UPF
ATOMIC_POSITIONS
C             0.0863    0.1169    0.0443
C             0.9137    0.8831    0.1321
C             0.9910    0.1450    0.0443
C             0.0090    0.8550    0.1321
C             0.8556    0.0163    0.0443
C             0.1444    0.9837    0.1321
C             0.8789    0.9197    0.0443
C             0.1211    0.0803    0.1321
C             0.0581    0.8668    0.0443
C             0.9419    0.1332    0.1321
C             0.1301    0.9353    0.0443
C             0.8699    0.0647    0.1321

K_POINTS automatic
  1 1 10   1 1 1

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.

-- 

Naiwrit Karmodak
Research Scholar,
C/o Prof E. D. Jemmis.
Inorganic and Physical Chemistry,
Indian Institute of Science, Bangalore-560012
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