[Pw_forum] error in finite electric field

[umari at democritos.it]

Dear Hongkien,

>    I have beening calculating the ferroelectic properties of BaTiO3
> under finite electric field, but in the scf cycle the code always
> crashed without giving any suggestions.I found the related error in the
> output file like this:
>
> iteration #  1     ecut=    35.00 Ry     beta=0.30
>     Davidson diagonalization with overlap
>  error hepsiher: translated G=  0.291666666666667
> 0.583333333333333      0.000000000000000E+000  with crystal 
> coordinates           0
> 1
>           0  corresponds to ng=           6  but G(ng)=
> 0.000000000000000E+000
>   1.00000000000000       0.000000000000000E+000
>  probably because G_par is NOT a reciprocal lattice vector
>  Possible choices as smallest  G_par:
>  i=           1    G=  0.000000000000000E+000  0.000000000000000E+000
>  0.000000000000000E+000
>  i=           2    G=  0.000000000000000E+000  0.000000000000000E+000
> -0.986981711228891      i=           3    G=  0.000000000000000E+000  
> 0.000000000000000E+000
>  0.986981711228891     .......

> I have tried different Kponts structure and the diagonalization
> methods,but failed. Is it a pseudopotential problem? It will be very
> appreciated for any suggestion about this. Thank you in advance.

As explained in the README of example 31 the direction of the electric 
field is given by gdir, note that till now
only orthorombic cells have been tested and gdir==3 is the only choice 
working for parallel calculations,
then nppstr gives the number of equally spaced k-point along the direction
gdir, which must be give in appropriate order.

In your case you have a mesh of 4 k-points along the second direction
but in the input file nppstr is 7 instead of 4 and gdir is 3 instead of 2

Best regards,
Paolo Umari,

DEMOCRITOS, Italy

> My input file was pasted here:
> &control
> calculation='scf'
> restart_mode='restart'
> prefix='bto',
> verbosity='high',
> pseudo_dir='./',
> outdir='./',
> gdir=3,
> nppstr=7,
> lelfield=.true.,
> nberrycyc=3,
> /
> &system
> ibrav= 6,
> celldm(1)= 7.6153,
> celldm(3)= 1.01319,
> nat= 5,
> ntyp= 3,
> lda_plus_u=.true.
> Hubbard_U(2)=4.3
> ecutwfc= 35.0,
> nosym=.true
> /
> &electrons
> mixing_beta=0.3,
> conv_thr= 1e-8,
> efield=0.001,
> startingwfc='random'
> /
> ATOMIC_SPECIES
> Ba  137.327  Ba.pbe-nsp-van.UPF
> Ti  47.88  Ti.pbe-sp-van_ak.UPF
> O   15.999     O.pbe-van_ak.UPF
> ATOMIC_POSITIONS  {crystal}
> Ba  0.00000     0.00000     0.00000
> Ti  0.50000   0.50000   0.50000
> O   0.50000   0.50000   0.00000
> O   0.00000     0.50000   0.50000
> O   0.50000   0.00000     0.50000
> K_POINTS 16
> 0.0  0.0   0.0   1
> 0.0  0.25  0.0   1
> 0.0  0.50  0.0   1
> 0.0  0.75  0.0   1
> 0.25 0.0   0.0   1
> 0.25 0.25  0.0   1
> 0.25 0.50  0.0   1
> 0.25 0.75  0.0   1
> 0.50 0.0   0.0   1
> 0.50 0.25  0.0   1
> 0.50 0.50  0.0   1
> 0.50 0.75  0.0   1
> 0.75 0.0   0.0   1
> 0.75 0.25  0.0   1
> 0.75 0.50  0.0   1
> 0.75 0.75  0.0   1


> Hongkien Feng

> physcis department,
> Beijing University of aeronautics & astronautics

----------------------------------------------------------------
This message was sent using IMP, the Internet Messaging Program.