The ABINIT Users Mailing List ( CLOSED )

[matthieu verstraete <matthieu.jean.verstraete@gmail.com>]

also your tsmear is quite large - you may be metallizing your system,
which could explain why there is no LOTO splitting...


On Wed, Sep 9, 2009 at 1:00 PM, matthieu
verstraete<matthieu.jean.verstraete@gmail.com> wrote:
> Search the forum for mails about the acoustic sum rule (ASR). You may
> have a problem with your pseudopotentials. Please follow the tutorial
> through fully (including anaddb) to get the LOTO splitting. And we
> need to see the output, eg how negative the modes are.
>
> Matthieu
>
> On Wed, Sep 9, 2009 at 9:12 AM, Sanjeev Kumar
> Gupta<skgupta.physics@gmail.com> wrote:
>> Dear sir,
>> Thanks for your quick answer, I have taken care of all optimization
>> parameters.
>> but, i did not got positive phonon frequencies.
>> regards
>> SKG
>>
>> 2009/9/9 Anglade Pierre-Matthieu <anglade@gmail.com>
>>>
>>> Hello,
>>>
>>> Frequently, unrelaxed cell parameters lead to negative phonon
>>> frequencies at gamma. Seeing your values for acell, I wonder if you
>>> have taken care to relax your cell structure using the same parameters
>>> (ecut, kpt, tsmear, occopt ...)  before trying to get phonon
>>> frequencies.
>>>
>>> Regards
>>>
>>> PMA
>>>
>>>
>>> On Wed, Sep 9, 2009 at 8:46 AM, Sanjeev Kumar
>>> Gupta<skgupta.physics@gmail.com> wrote:
>>> > Dear ABINIT users,
>>> > Greetings...
>>> >
>>> > I want to calculate phonon frequencies of GaP system (semiconductor),
>>> > the
>>> > input file, for that i got from abinit/tutorial.
>>> > when i run this file (input file is given below), i got negative phonon
>>> > frequencies at gamma point and no LO-TO separation.
>>> >
>>> > I have also given here, the output after running this input file. please
>>> > suggest me, where i am wrong? I have seen all earlier posting related
>>> > with
>>> > this subject, but i can not resolve this problem.
>>> >
>>> > kind regards
>>> > sanjeev
>>> >
>>> >
>>> >
>>> >
>>> > # Crystalline GaP : computation of the response to homogeneous
>>> >
>>> > # electric field and atomic displacements, at q=0
>>> >
>>> >
>>> >
>>> >
>>> >
>>> >
>>> >
>>> >   ndtset  3
>>> >
>>> >
>>> >
>>> >
>>> >
>>> > #Ground state calculation
>>> >
>>> >   kptopt1   1             # Automatic generation of k points, taking
>>> >
>>> >                           # into account the symmetry
>>> >
>>> >   tolvrs1   1.0d-20     # SCF stopping criterion
>>> >
>>> >     iscf1   7             # Self-consistent calculation, using algorithm
>>> > 7
>>> >
>>> >
>>> >
>>> >
>>> >
>>> > #Response Function calculation : d/dk
>>> >
>>> >   rfelfd2   2             # Activate the calculation of the d/dk
>>> > perturbation
>>> >
>>> >    rfdir2   1 1 1         # Need to consider the perturbation in the all
>>> > direction
>>> >
>>> >
>>> >
>>> >     nqpt2   1
>>> >
>>> >      qpt2   0.0 0.0 0.0   # This is a calculation at the Gamma point
>>> >
>>> >
>>> >
>>> >
>>> >
>>> >   getwfk2   -1            # Uses as input the output wf of the previous
>>> > dataset
>>> >
>>> >
>>> >
>>> >
>>> >
>>> >   kptopt2   2             # Automatic generation of k points,
>>> >
>>> >                           # using only the time-reversal symmetry to
>>> > decrease
>>> >
>>> >                           # the size of the k point set.
>>> >
>>> >
>>> >
>>> >
>>> >
>>> >     iscf2  -3             # The d/dk perturbation must be treated
>>> >
>>> >                               # in a non-self-consistent way
>>> >
>>> >   tolwfr2   1.0d-22       # Must use tolwfr for non-self-consistent
>>> > calculations
>>> >
>>> >
>>> >
>>> > #Response Function calculation : electric field perturbation and phonons
>>> >
>>> >   rfphon3   1             # Activate the calculation of the atomic
>>> > dispacement perturbations
>>> >
>>> >  rfatpol3   1 2          # All the atoms will be displaced
>>> >
>>> >   rfelfd3   3              # Activate the calculation of the electric
>>> > field
>>> > perturbation
>>> >
>>> >    rfdir3   1 1 1         # All directions are selected. However,
>>> > symmetries
>>> > will be used to decrease
>>> >
>>> >                                 # the number of perturbations
>>> >
>>> >     nqpt3   1
>>> >
>>> >      qpt3   0.0 0.0 0.0   # This is a calculation at the Gamma point
>>> >
>>> >
>>> >
>>> >
>>> >
>>> >   getwfk3   -2            # Uses as input wfs the output wfs of the
>>> > dataset
>>> > 1
>>> >
>>> >   getddk3   -1            # Uses as input ddk wfs the output of the
>>> > dataset
>>> > 2
>>> >
>>> >
>>> >
>>> >
>>> >
>>> >   kptopt3   2             # Automatic generation of k points,
>>> >
>>> >                           # using only the time-reversal symmetry to
>>> > decrease
>>> >
>>> >                           # the size of the k point set.
>>> >
>>> >   tolvrs3   1.0d-9
>>> >
>>> >     iscf3   7             # Self-consistent calculation, using algorithm
>>> > 7
>>> >
>>> >
>>> >
>>> >
>>> >
>>> >
>>> >
>>> >
>>> >
>>> > #######################################################################
>>> >
>>> > #Common input variables
>>> >
>>> >
>>> >
>>> >
>>> >
>>> > #Definition of the unit cell
>>> >
>>> > acell 3*10.45          # This is equivalent to   10.61 10.61 10.61
>>> >
>>> > rprim  0.0  0.5  0.5
>>> >
>>> >        0.5  0.0  0.5
>>> >
>>> >        0.5  0.5  0.0
>>> >
>>> >
>>> >
>>> >
>>> >
>>> > #Definition of the atom types
>>> >
>>> > ntypat 2               # There are two types of atom
>>> >
>>> > znucl 31 15
>>> >
>>> >
>>> >
>>> >
>>> >
>>> > #Definition of the atoms
>>> >
>>> > natom 2                # There are two atoms
>>> >
>>> > typat 1 2
>>> >
>>> > xred
>>> >
>>> >    0.0  0.0  0.0
>>> >
>>> >    0.25 0.25 0.25
>>> >
>>> >
>>> >
>>> >
>>> >
>>> > #Gives the number of band, explicitely
>>> >
>>> > nband  16
>>> >
>>> >
>>> >
>>> >
>>> >
>>> > #Exchange-correlation functional
>>> >
>>> > ixc 11
>>> >
>>> > #Definition of the planewave basis set
>>> >
>>> >  ecut    50.0           # Maximal kinetic energy cut-off, in Hartree
>>> >
>>> >
>>> >
>>> >
>>> >
>>> > #Definition of the k-point grid
>>> >
>>> > kptrlatt -4  4  4      # In cartesian coordinates, this grid is simple
>>> > cubic, and
>>> >
>>> >           4 -4  4       # actually corresponds to the so-called 8x8x8
>>> > Monkhorst-Pack grid.
>>> >
>>> >           4  4 -4
>>> >
>>> >           tsmear   0.04
>>> >
>>> >           occopt   4
>>> >
>>> >
>>> >
>>> >
>>> >
>>> >
>>> >
>>> > #Definition of the SCF procedure
>>> >
>>> > nstep 100               # Maximal number of SCF cycles
>>> >
>>> > diemac 10.0
>>> >
>>> >
>>> >
>>> >  
>>> > ............................................................................................
>>> >
>>> > ouput
>>> >
>>> >
>>> > Phonon wavevector (reduced coordinates) :  0.00000  0.00000  0.00000
>>> >
>>> >  Phonon energies in Hartree :
>>> >
>>> >   -1.028821E-04 -1.028819E-04 -1.028810E-04  1.468314E-03  1.468314E-03
>>> >
>>> >    1.468314E-03
>>> >
>>> >  Phonon frequencies in cm-1    :
>>> >
>>> > - -2.258001E+01 -2.257997E+01 -2.257978E+01  3.222577E+02  3.222577E+02
>>> >
>>> > -  3.222577E+02
>>>
>>>
>>>
>>> --
>>> Pierre-Matthieu Anglade
>>>
>>
>>
>>
>> --
>> S. K. Gupta
>> PhD Candidate,
>> Dept. of Physics, Bhavnagar University.
>> Bhavnagar, 364 022., Gujarat, India.
>>
>>
>>
>>
>
>
>
> --
> ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> Dr. Matthieu Verstraete
>
> Universite de Liège
> Institut de Physique, Bat. B5
> Allée du 6 aout, 17
> B- 4000 Sart Tilman, Liège
> Belgium
>
> Phone : +32 4 366 37 50
> Fax   : +32 4 366 36 29
>
> Mail : matthieu.jean.verstraete@gmail.com
>



-- 
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Dr. Matthieu Verstraete

Universite de Liège
Institut de Physique, Bat. B5
Allée du 6 aout, 17
B- 4000 Sart Tilman, Liège
Belgium

Phone : +32 4 366 37 50
Fax   : +32 4 366 36 29

Mail : matthieu.jean.verstraete@gmail.com