[Pw_forum] erro wrong attomic cordinates for 5-0 nanotub

[Axel Kohlmeyer]

On Sun, 9 Dec 2007, meisam aghtar wrote:

MA> Dear all

dear meisam,

MA> during optimizing the a lattice in a zigzag nanotube there was a 
MA> problem , the run for celldm(1) is done but for the upper cell 
MA> dimensions it stops and the error is : wrong atomic cordinates. of 

this usually means, that atom positions do overlap.
did you check for this?


MA> cours in the output file of the former is written : davidson 
MA> diagnolization with overlap . I don't know if it makes problem.

no.

what is odd, that you write you want to optimize the lattice,
but you specify _absolute_ coordinates (in angstrom). this way
only the box dimensions change, not that (relative) atom positions.
when people usually say, they want to optimize the lattice, they
mean, that they want to find the optimal lattice parameter and 
then they use relative positions (alat or crystal units). absolute
coordinates make sense, when you want to "optimize" the vacuum
around a cluster. with a nanotube system, though, you have both.

please check, whether your input makes sense (-> xcrysden)
and then try to explain a bit more clearly what you want to
do, if you still have problems.

cheers,
    axel.

p.s.: are you sure a 30ry plane wave energy cutoff is sufficient
for the type of pseudopotential (norm-conserving) you are using?
no point in trying to optimize lattice parameter when your basis
set is incomplete...

MA> input:
MA> &CONTROL
MA>                  calculation = 'scf' ,
MA>                 restart_mode = 'restart' ,
MA>                       outdir = '/home/meisam/projhe/5-0/band/scratch/' ,
MA>                   pseudo_dir = '/home/meisam/espresso-3.1.1/pseudo/' ,
MA>                       prefix = 'cnt18-scf' ,
MA>  /
MA>  &SYSTEM
MA>                        ibrav = 4,
MA>                    celldm(1) = 18,
MA>                    celldm(3) = 0.447232826,
MA>                          nat = 25,
MA>                         ntyp = 1,
MA>                      ecutwfc = 30 ,
MA>  /
MA>  &ELECTRONS
MA>  /
MA> ATOMIC_SPECIES
MA>     C   12.00000  C.pz-vbc.UPF
MA> ATOMIC_POSITIONS angstrom
MA>     C      1.958200000    0.000000000   -1.420000000

[...]


-- 
=======================================================================
Axel Kohlmeyer   akohlmey at cmm.chem.upenn.edu   http://www.cmm.upenn.edu
   Center for Molecular Modeling   --   University of Pennsylvania
Department of Chemistry, 231 S.34th Street, Philadelphia, PA 19104-6323
tel: 1-215-898-1582,  fax: 1-215-573-6233,  office-tel: 1-215-898-5425
=======================================================================
If you make something idiot-proof, the universe creates a better idiot.