[Pw_forum] problem in optimizing nanotubes in QE

[Bahadır salmankurt]

Dear Naiwrit Karmodak,

For these structure type, such as slab or tube,  mixing_mode 'plain' is not
suitable. Please use 'LOCAL-TF' instead of 'Plain' Also decreasing
degauss(0.001) effect the converge in a good way and for better results ,
the value of  conv_thr  can be taken 1.0D-8 or less,

kind regards

2015-09-16 6:16 GMT+03:00 Naiwrit Karmodak <knaiwrit at gmail.com>:

> 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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>



-- 

Bahadır SALMANKURT
Sakarya University, TURKEY
Ph.D. student of Physics
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