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["Larry E. Johnson" <gridphysics@hotmail.com>]

Tula,
I changed your input data slightly, correcting your xred from 0.5 to 0.25, and for me also to make the run finish faster, I used tolvrs1 not 1.0d-22 but 1.0d-08, and nstep (number of SCF steps) not 100 but just 15 like the tutorial trf1.  This correction lifts the phonon frequency degeneracy where it should now:  I get at vector 0,0,0  the cm^-1 of 4.825642E+00  5.834103E+00  5.989694E+00  7.901520E+02,  same,  same.   So I think this is in the right ball park with 21-Sc_pspnc.txt and 07-N_LDA_fhi.txt
Larry

> Date: Fri, 30 May 2008 20:39:00 +0200
> To: forum@abinit.org
> From: trp6@case.edu
> Subject: [abinit-forum] Psedopotential diff phonons ?
>
> Dear all,
>
> I am trying to calculate the phonon modes of ScN using LDA.fhi and pspnc pseudo
> potential. But the result is quite different.
>
> Here are the parts form my output obtained with pspnc and fhi only
> respectively.
> - 2.989980E+00 2.989980E+00 2.989980E+00 2.729446E+02 2.729446E+02
> - 2.729446E+02
>
> Phonon frequencies in cm-1 :
> - 2.989980E+00 2.989980E+00 2.989980E+00 2.729446E+02 2.729446E+02
> - 2.729446E+02
>
> Similar order of difference persist in other q points also.
>
> I am surprised to see that much difference after all both being LDA
> Troullier-Martins psp.
> Any suggestion, why ?, and which to trust. I earlier did calculation with fhi
> psp they give the resonable phonon in AlN, GaN. But In this case since
> experiment is not so clear, I am not sure what to trust.
>
> Further I obtained the similar result with LuN.
>
> One more question, might be related with it. Why there is use of fhi and pspnc
> psp for Al and As in tutorial of AlAs in Response function. Seems like don't
> made much difference but any particular reason ?
>
> I used ixc 1 with pspnc and ixc 7 with fhi.
>
> And here is my input file.
>
> # Crystalline Scn : computation of the phonon spectrum
>
>
> ndtset 18
> #Set 1 : ground state self-consistency
>
>
> getwfk1 0 # Cancel default
> kptopt1 1 # Automatic generation of k points, taking
> # into account the symmetry
> nqpt1 0 # Cancel default
> tolvrs1 1.0d-22 # SCF stopping criterion (modify default)
> rfphon1 0 # Cancel default
>
>
> #Q vectors for all datasets
>
>
> #Complete set of symmetry-inequivalent qpt chosen to be commensurate
> # with kpt mesh so that only one set of GS wave functions is needed.
> #Generated automatically by running GS calculation with kptopt=1,
> # nshift=0, shiftk=0 0 0 (to include gamma) and taking output kpt set
> # file as qpt set. Set nstep=1 so only one iteration runs.
>
>
> nqpt 1 # One qpt for each dataset (only 0 or 1 allowed)
> # This is the default for all datasets and must
> # be explicitly turned off for dataset 1.
>
>
> qpt2 0.00000000E+00 0.00000000E+00 0.00000000E+00
> qpt3 0.00000000E+00 0.00000000E+00 0.00000000E+00
> qpt4 1.66666667E-01 0.00000000E+00 0.00000000E+00
> qpt5 3.33333333E-01 0.00000000E+00 0.00000000E+00
> qpt6 5.00000000E-01 0.00000000E+00 0.00000000E+00
> qpt7 1.66666667E-01 1.66666667E-01 0.00000000E+00
> qpt8 3.33333333E-01 1.66666667E-01 0.00000000E+00
> qpt9 5.00000000E-01 1.66666667E-01 0.00000000E+00
> qpt10 -3.33333333E-01 1.66666667E-01 0.00000000E+00
> qpt11 -1.66666667E-01 1.66666667E-01 0.00000000E+00
> qpt12 3.33333333E-01 3.33333333E-01 0.00000000E+00
> qpt13 5.00000000E-01 3.33333333E-01 0.00000000E+00
> qpt14 -3.33333333E-01 3.33333333E-01 0.00000000E+00
> qpt15 5.00000000E-01 5.00000000E-01 0.00000000E+00
> qpt16 5.00000000E-01 3.33333333E-01 1.66666667E-01
> qpt17 -3.33333333E-01 3.33333333E-01 1.66666667E-01
> qpt18 -3.33333333E-01 5.00000000E-01 1.66666667E-01
>
> #Set 2 : Response function calculation of d/dk wave function
>
>
> iscf2 -3 # Need this non-self-consistent option for d/dk
> kptopt2 2 # Modify default to use time-reversal symmetry
> rfphon2 0 # Cancel default
> rfelfd2 2 # Calculate d/dk wave function only
> tolvrs2 0.0 # Cancel default for d/dk
> tolwfr2 1.0d-22 # Use wave function residual criterion instead
>
>
> #Set 3 : Response function calculation of Q=0 phonons and electric field pert.
>
>
> getddk3 2 # d/dk wave functions from last dataset
> kptopt3 2 # Modify default to use time-reversal symmetry
> rfelfd3 3 # Electric-field perturbation response only
>
>
> #Sets 4-10 : Finite-wave-vector phonon calculations (defaults for all datasets)
>
>
> getwfk 1 # Use GS wave functions from dataset1
> kptopt 3 # Need full k-point set for finite-Q response
> rfphon 1 # Do phonon response
> rfatpol 1 2 # Treat displacements of all atoms
> rfdir 1 1 1 # Do all directions (symmetry will be used)
> tolvrs 1.0d-8 # This default is active for sets 3-10
>
>
> #######################################################################
> #Common input variables
>
>
> #Definition of the unit cell
> acell 3*8.49525 # is equivalent to 3*8.50
> rprim 0.0 0.5 0.5 # In lessons 1 and 2, these primitive vectors
> 0.5 0.0 0.5 # (to be scaled by acell) were 1 0 0 0 1 0 0 0 1
> 0.5 0.5 0.0 # that is, the default.
>
>
> #Definition of the atom types
> ntypat 2 # There are two types of atom
> znucl 21 7 # 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, type 1 is the Aluminum,
> # type 2 is the Arsenic.
>
>
> #Definition of the atoms
> natom 2 # There are two atoms
> typat 1 2 # The first is of type 1 (Al), the second is of type 2
> (As).
>
>
> xred 0.0 0.0 0.0
> 0.5 0.5 0.5
>
>
> #Gives the number of band, explicitely (do not take the default)
> nband 4
>
>
> #Exchange-correlation functional
>
>
> ixc 1
>
>
> #Definition of the planewave basis set
>
>
> ecut 40.0 # Maximal kinetic energy cut-off, in
> Hartree#Definition of the k-point grid
> ngkpt 6 6 6
> nshiftk 4 # Use one copy of grid only (default)
> shiftk 0.0 0.0 0.5 # This gives the usual fcc Monkhorst-Pack grid
> 0.0 0.5 0.0
> 0.5 0.0 0.0
> 0.5 0.5 0.5
> #Definition of the SCF procedure
> iscf 5 # Self-consistent calculation, using algorithm 5
> nstep 100 # Maximal number of SCF cycles
>
> Thanks.

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