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["Anglade Pierre-Matthieu" <anglade@gmail.com>]

Hi,

Your preconditioning is not correct. There is two problem with it:
your nanotube is metallic so you must expect a higher value for diemac
and your cell is not homogeneous (lots of vacuum). You'd better use
"iprcel 49" instead of "diemac 12" it will certainly helps a lot.

regards

PMA

On 6/15/06, yshtogun@cas.usf.edu <yshtogun@cas.usf.edu> wrote:
> Convergence
>  Dear ABINIT users!
>   I try to calculate Etotal for metal carbon nanotubes, but I was not able to 
> reach convergence. I saw that in my output file Etotal starts wobbling around 
> some value, I looked at lesson for Al  and did the same way.  There is my out 
> put file:
>
>  ETOT 81  -138.61248625690    -1.621E-02 7.759E-02 4.898E+03 7.247E-02 
> 6.434E-02
>  ETOT 82  -138.59572056047     1.677E-02 8.067E-02 4.905E+03 7.189E-02 
> 6.463E-02
>  ETOT 83  -138.59789426457    -2.174E-03 9.536E-02 4.916E+03 7.272E-02 
> 6.541E-02
>  ETOT 84  -138.59854520570    -6.509E-04 8.775E-02 4.917E+03 7.350E-02 
> 6.541E-02
>  ETOT 85  -138.59404342836     4.502E-03 9.851E-02 4.921E+03 7.384E-02 
> 6.486E-02
>  ETOT 86  -138.59218749179     1.856E-03 9.981E-02 4.921E+03 7.315E-02 
> 6.471E-02
>  ETOT 87  -138.58897216161     3.215E-03 1.020E-01 4.922E+03 7.301E-02 
> 6.429E-02
>  ETOT 88  -138.59681906813    -7.847E-03 1.188E-01 4.918E+03 7.280E-02 
> 6.450E-02
>  ETOT 89  -138.60192171587    -5.103E-03 1.160E-01 4.911E+03 7.209E-02 
> 6.342E-02
>  ETOT 90  -138.63243709379    -3.052E-02 1.452E-01 4.891E+03 7.288E-02 
> 6.528E-02
>  ETOT 91  -138.67069938233    -3.826E-02 1.283E-01 4.855E+03 7.464E-02 
> 6.543E-02
>  ETOT 92  -138.65744598321     1.325E-02 9.016E-02 4.839E+03 7.518E-02 
> 6.583E-02
>  ETOT 93  -138.69142100515    -3.398E-02 1.003E-01 4.840E+03 7.397E-02 
> 6.380E-02
>  ETOT 94  -138.67800496752     1.342E-02 1.362E-01 4.844E+03 7.331E-02 
> 6.517E-02
>  ETOT 95  -138.78701676235    -1.090E-01 1.661E-01 4.777E+03 7.236E-02 
> 5.931E-02
>  ETOT 96  -138.81659394107    -2.958E-02 8.866E-02 4.738E+03 7.003E-02 
> 6.284E-02
>  ETOT 97  -138.76127302580     5.532E-02 1.127E-01 4.780E+03 7.247E-02 
> 6.457E-02
>  ETOT 98  -138.83699500452    -7.572E-02 1.895E-01 4.735E+03 7.125E-02 
> 6.081E-02
>  ETOT 99  -138.84379116069    -6.796E-03 8.810E-02 4.714E+03 7.024E-02 
> 6.172E-02
>  ETOT100  -138.78397012486     5.982E-02 1.138E-01 4.761E+03 7.426E-02 
> 6.483E-02
>
> My input file:
> # (6,6) Carbon Nanotube : computation of the total energy
> # bond legth a = 1.419 angstrom 1 unit cell
> # the potential files - 6c.pspnc LDA (Troullier - Martins)
>
>
> #Definition of the unit cell
> acell 48.7816266774 48.7816266774 2.4577800959  angstrom    # The size of 
> unit cell in angstrom
>
>
> #Definition of the atom types
> ntypat 1          # There is only one type of atom
> znucl 6           # The keyword "znucl" refers to the atomic number of the
>                   # possible type(s) of atom. The pseudopotential(s)
>                   # mentioned in the "files" file must correspond
>                   # to the type(s) of atom. Here, the only type is Silicon.
>
>
> #Definition of the atoms
> natom 24          # There are 24 atoms
> typat 24*1
>                   # They all are of type 1, that is, Carbon.
>
> xangst            # This keyword indicate that the location of the atoms
>                   # will follow, one triplet of number for each atom
>                   # Triplet giving the cartesian coordinates of all atoms, in 
> Angstrom
> 28.4559489387  24.3908133387  0.0000000000
> 28.2107912387  25.7811715387  0.0000000000
> 26.4233811387  27.9113240387  0.0000000000
> 25.0967167387  28.3941903387  0.0000000000
> 22.3582455387  27.9113240387  0.0000000000
> 21.2767388387  27.0038321387  0.0000000000
> 20.3256777387  24.3908133387  0.0000000000
> 20.5708354387  23.0004551387  0.0000000000
> 22.3582455387  20.8703026387  0.0000000000
> 23.6849099387  20.3874363387  0.0000000000
> 26.4233811387  20.8703026387  0.0000000000
> 27.5048878387  21.7777945387  0.0000000000
> 27.9113240387  26.4233811387  1.2288900000
> 27.0038321387  27.5048878387  1.2288900000
> 24.3908133387  28.4559489387  1.2288900000
> 23.0004551387  28.2107912387  1.2288900000
> 20.8703026387  26.4233811387  1.2288900000
> 20.3874363387  25.0967167387  1.2288900000
> 20.8703026387  22.3582455387  1.2288900000
> 21.7777945387  21.2767388387  1.2288900000
> 24.3908133387  20.3256777387  1.2288900000
> 25.7811715387  20.5708354387  1.2288900000
> 27.9113240387  22.3582455387  1.2288900000
> 28.3941903387  23.6849099387  1.2288900000
>
> #Definition of the planewave basis set
> ecut  20.0         # Maximal kinetic energy cut-off, in Hartree
>
> #Exchange-correlation functional
> ixc 1             # LDA Teter Pade parametrization
> #iscf 2
>
> ecutsm 0.5
>
> #Definition of the k-point grid
> kptopt 1          # Option for the automatic generation of k points, taking
>                   # into account the symmetry
> ngkpt 1 1 4       # This is a 1x1x4 grid based on the primitive vectors
> nshiftk 1
> shiftk  0 0 0.5
>
>
> #Definition of the SCF procedure
> nstep 100         # Maximal number of SCF cycles
> toldfe 1.0d-6     # Will stop when, twice in a row, the difference
>                   # between two consecutive evaluations of total energy
>                   # differ by less than toldfe (in Hartree)
> diemac 12.0       # Although this is not mandatory, it is worth to
>                   # precondition the SCF cycle. The model dielectric
>                   # function used as the standard preconditioner
>                   # is described in the "dielng" input variable section.
>                   # Here, we follow the prescription for carbon.
>
>                Should I specify some other parameters?
>         I appreciate all suggestion and comments.
>
>   Thank you in advance!
>
>   Yaroslav!


--
Pierre-Matthieu Anglade