The ABINIT Users Mailing List ( CLOSED )

["Aldo Humberto Romero" <aromero@qro.cinvestav.mx>]

Dear Sanjeev

what are the stresses?.. this will indicate how well converged
you are.. but just looking at your acell, with only two digits,
probably is not.
I see it is a Zb structure, read about how to choose K points
for those.. just in case... we have done many different Zb and Rs
structures and never encounter a problem as the one you mention

regards

-aldo.


-> 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
->


-- 

Prof. Aldo Humberto Romero
CINVESTAV-Unidad Queretaro
Libramiento Norponiente 2000
CP 76230, Queretaro, QRO, Mexico
tel: 442 211 9909
fax: 442 211 9938

email: aromero@qro.cinvestav.mx
        aldorome@gmail.com
www: qro.cinvestav.mx/~aromero