The ABINIT Users Mailing List ( CLOSED )

[pascal boulet <pascal.boulet@univ-provence.fr>]

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Dear Igor,

Here are a few remarks from a first glance at your input file.


* First I would decrease the value of tolvrs down to 1d-20 or 1d-22.
* Second and perhaps most important: are you sure about the cell
parameter? I am working with Mg2Si (same kind of structure) and the
"a" parameter is around 11 bohrs.  I expect ZrO2 to have a bigger
cell, but I might be wrong... In any case, the cell parameter should
be the one of the unit cell, not that the primitive cell. If the cell
is too small, you constraint the system that becomes unstable and this
leads to imaginary phonon frequencies. But I guess you know this.
I found that the cell parameters of tetragonal ZrO2 are about
5.3*5.2*5.1 angstroms which should not drastically be different from
the cubic structure.  My guess is that you forgot to specify
"angstrom"  after the value of "a". The default is bohr.
* the worst case would be that the pseudopotentials are suitable for
the gamma points only. So, you also have to check this.

Hope this help,
Best regards
Pascal



Igor Lukacevic a écrit :
> Dear colleagues,
>
> I am having problems in reproducing the phonon dispersions in the
> rocksalt phase of ZrO2 wrt the results obtained in F. Detraux et
> al., prl 81, 3297 (1998):
>
> 1] I obtain many imaginary frequencies. 2] Acoustic mode(s) go
> imaginary, while the optical mode is the unstable one.
>
> They have been using ecut 30 Ha and ngkpt 3*4, while I used ecut 60
>  Ha and ngkpt 3*6. Both psuedos have the same number of valence
> electrons.
>
> I'm using abinit 5.8.4p, and I correct the output of mrgdbb (acell
> and rprim) to be able to use brav=2 option in anaddb. My calcs
> converge without warnings. I'm sending the inputs and the plot
> bellow.
>
> Could anyone give me a clue why this happens and how to improve my
> calcs?
>
> Thank you all in advance!
>
> Yours,
>
> Igor Lukacevic
>
>
>
> ================================== RF phonon input
>
> # Crystalline ZrO2 - fluorite - cubic fcc - Fm-3m #225 :
> 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-18
> # 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 4-17 : 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 3        # 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*9.46 angdeg   90  90  90
> brvltt  -1 spgroup   225
>
> #Definition of the atom types ntypat   2 znucl   40 8 8
>
> #Definition of the atoms natom   3 typat   1 2 2
>
> xred   0.00  0.00  0.00 0.25  0.25  0.25 0.75  0.75  0.75
>
> #Gives the number of band, explicitely (do not take the default)
> nband   14
>
> #Exchange-correlation functional
>
> ixc   3
>
> #Definition of the planewave basis set
>
> ecut   60
>
> #Definition of the k-point grid nshiftk   4 shiftk    0.5  0.5  0.5
>  0.5  0.0  0.0 0.0  0.5  0.0 0.0  0.0  0.5 ngkpt     3*6
>
> #Definition of the SCF procedure iscf    7              # Use Pulay
> mixing sheme for SCF cycle npulayit    10             # Number of
> Pulay iterations nnsclo    4              # Number of non-self
> consistent loops nline    8              # Number of line
> minimisations
>
> diemac    4
>
>
> ================================== anaddb input
>
> !Input file for the anaddb code. Analysis of the SiO2 DDB
>
>
> !Flags ifcflag   1     ! Interatomic force constant flag
>
> !Wavevector grid number 1 (coarse grid, from DDB) brav    2      !
> Bravais Lattice : 1-S.C., 2-F.C., 3-B.C., 4-Hex.) ngqpt   3*6    !
> Monkhorst-Pack indices nqshft  1      ! number of q-points in
> repeated basic q-cell q1shft  3*0.0
>
> !Effective charges asr   1     ! Acoustic Sum Rule. 1 => imposed
> asymetrically chneut   1     ! Charge neutrality requirement for
> effective charges.
>
> !Interatomic force constant info dipdip  1      ! Dipole-dipole
> interaction treatment
>
> !Phonon band structure output for band2eps - See note near end for
> ! dealing with gamma LO-TO splitting issue. eivec  4
>
> !Wavevector list number 1 (Reduced coordinates and normalization
> factor) nph1l   71     ! number of phonons in list 1
>
>
> qph1l   0.0000  0.0000  0.0000   1.0    !(gamma point) 0.0375
> 0.0375  0.0750   1.0 0.0750  0.0750  0.1500   1.0 0.1125  0.1125
> 0.2250   1.0 0.1500  0.1500  0.3000   1.0 0.1875  0.1875  0.3750
> 1.0 0.2250  0.2250  0.4500   1.0 0.2625  0.2625  0.5250   1.0
> 0.3000  0.3000  0.6000   1.0 0.3375  0.3375  0.6750   1.0 0.3750
> 0.3750  0.7500   1.0    !(K point) 0.3875  0.3875  0.7750   1.0
> 0.4000  0.4000  0.8000   1.0 0.4125  0.4125  0.8250   1.0 0.4250
> 0.4250  0.8500   1.0 0.4375  0.4375  0.8750   1.0 0.4500  0.4500
> 0.9000   1.0 0.4625  0.4625  0.9250   1.0 0.4750  0.4750  0.9500
> 1.0 0.4875  0.4875  0.9750   1.0 0.5000  0.5000  1.0000   1.0
> !(X point) 0.5500  0.5500  1.0000   1.0 0.6000  0.6000  1.0000
> 1.0 0.6500  0.6500  1.0000   1.0 0.7000  0.7000  1.0000   1.0
> 0.7500  0.7500  1.0000   1.0 0.8000  0.8000  1.0000   1.0 0.8500
> 0.8500  1.0000   1.0 0.9000  0.9000  1.0000   1.0 0.9500  0.9500
> 1.0000   1.0 1.0000  1.0000  1.0000   1.0    !(gamma point) 0.9500
> 0.9500  0.9500   1.0 0.9000  0.9000  0.9000   1.0 0.8500  0.8500
> 0.8500   1.0 0.8000  0.8000  0.8000   1.0 0.7500  0.7500  0.7500
> 1.0 0.7000  0.7000  0.7000   1.0 0.6500  0.6500  0.6500   1.0
> 0.6000  0.6000  0.6000   1.0 0.5500  0.5500  0.5500   1.0 0.5000
> 0.5000  0.5000   1.0    !(L point) 0.5000  0.4500  0.5000   1.0
> 0.5000  0.4000  0.5000   1.0 0.5000  0.3500  0.5000   1.0 0.5000
> 0.3000  0.5000   1.0 0.5000  0.2500  0.5000   1.0 0.5000  0.2000
> 0.5000   1.0 0.5000  0.1500  0.5000   1.0 0.5000  0.1000  0.5000
> 1.0 0.5000  0.0500  0.5000   1.0 0.5000  0.0000  0.5000   1.0
> !(X point) 0.5000  0.0250  0.5250   1.0 0.5000  0.0500  0.5500
> 1.0 0.5000  0.0750  0.5750   1.0 0.5000  0.1000  0.6000   1.0
> 0.5000  0.1250  0.6250   1.0 0.5000  0.1500  0.6500   1.0 0.5000
> 0.1750  0.6750   1.0 0.5000  0.2000  0.7000   1.0 0.5000  0.2250
> 0.7250   1.0 0.5000  0.2500  0.7500   1.0    !(W point) 0.5000
> 0.2750  0.7250   1.0 0.5000  0.3000  0.7000   1.0 0.5000  0.3250
> 0.6750   1.0 0.5000  0.3500  0.6500   1.0 0.5000  0.3750  0.6250
> 1.0 0.5000  0.4000  0.6000   1.0 0.5000  0.4250  0.5750   1.0
> 0.5000  0.4500  0.5500   1.0 0.5000  0.4750  0.5250   1.0 0.5000
> 0.5000  0.5000   1.0    !(L point)
>
> !Wavevector list number 2 (Cartesian directions for non-analytic
> gamma phonons)
>
> !The output for this calculation must be cut-and-pasted into the !
> t59_out.freq file to be used as band2eps input to get proper LO-TO
> ! splitting at gamma.  Note that gamma occurrs twice.
>
> nph2l    1       ! number of directions in list 2
>
> qph2l   1.0  0.0  0.0    0.0 # This line added when defaults were
> changed (v5.3) to keep the previous, old behaviour symdynmat 0

- --
Dr. pascal Boulet, computational chemist
Laboratoire Chimie Provence, UMR 6264
University of Aix-Marseille I
Avenue Escadrille Normandie-Niemen
13397 Marseille Cedex 20
France
**********
Tel. (+33) (0)491.63.71.17
Fax. (+33) (0)491.63.71.11
**********
http://www.lc-provence.fr
http://allos.up.univ-mrs.fr/boulet
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