The ABINIT Users Mailing List ( CLOSED )

["Matteo Giantomassi" <Matteo.Giantomassi@uclouvain.be>]

>   Dear forum users,
> I'm following tutor of RF2 and calculating phonon dispersion curve and
> PDOS for PbTe. The psudopotential files are 82pb.pspnc and
> 52te.pspnc(LDA), ecut 30, ngkpt 3*4.  The curious thing is that abinit
> gave out negative  Phonon energy and frequency in the output file as
> following;
>
> Phonon wavevector (reduced coordinates) :  0.00000  0.00000  0.00000
>  Phonon energies in Hartree :
>   -2.656610E-07 -2.656575E-07 -2.656473E-07  2.114512E-04  2.114512E-04
>    2.114512E-04
>
> But after analyzed ddb anaddb gave out zero Phonon energy and frequency at
> gamma.
>
>   Phonon at Gamma, with non-analyticity in the
>   direction (cartesian coordinates)  1.00000  0.00000  0.00000
>  Phonon energies in Hartree :
>    0.000000E+00  0.000000E+00  0.000000E+00  2.114513E-04  2.114514E-04
>    4.680436E-04
>  Phonon frequencies in cm-1    :
> -  0.000000E+00  0.000000E+00  0.000000E+00  4.640819E+01  4.640822E+01
> -  1.027237E+02
>
> Is it natural or not?
> What's more, I use prtdos 1 to print the PDOS. But the output PHDOS has
> omiga from -0.29933    to 17.18245  and the total distribution isn't
> right. Is there anything wrong?
> The two input files are as following. Any comments will be appreciated.
> Thank you in advance.
>
 Dear Shelleny,

 What do you mean with "is not right"?
 Are you are trying to reproduce previous calculations?

 Note that the non-zero PHDOS at imaginary frequencies might be due to phonon
 instabilities in the Brillouin zone (non necessarily at Gamma).
 These vibrational instabilities might appear after the Fourier
interpolation of the
 dynamical matrix on the dense q-mesh used to calculate the density of
states.
 Did you plot the phonon dispersion along high symmetry lines in the BZ?

 Best Regards,
 Matteo Giantomassi


> Best regards,
> shelleny
>
> #####abinis input file:#####################
> ndtset 10
> #Datasets 1 : GS
> getwfk1 0
> kptopt1 1
> nqpt1 0
> tolvrs1 1.0d-18
> rfphon1 0
> #q vectors
> nqpt 1
>      qpt2   0.00000000E+00  0.00000000E+00  0.00000000E+00
>      qpt3   0.00000000E+00  0.00000000E+00  0.00000000E+00
>      qpt4   2.50000000E-01  0.00000000E+00  0.00000000E+00
>      qpt5   5.00000000E-01  0.00000000E+00  0.00000000E+00
>      qpt6   2.50000000E-01  2.50000000E-01  0.00000000E+00
>      qpt7   5.00000000E-01  2.50000000E-01  0.00000000E+00
>      qpt8  -2.50000000E-01  2.50000000E-01  0.00000000E+00
>      qpt9   5.00000000E-01  5.00000000E-01  0.00000000E+00
>      qpt10 -2.50000000E-01  5.00000000E-01  2.50000000E-01
> #Dataset 2 : ddk
>  rfelfd2   2
>  rfphon2   0
>  kptopt2   2
>  iscf2     -3
> tolvrs2 0.0
> tolwfr2 1.0d-22
> #Dataset 3: electric field + phonon response at gamma
>  rfelfd3  3
>  getddk3  -1
>  kptopt3   2
> #Dataset 4-74: phonon perturb
> getwfk 1
> kptopt 3
> rfphon 1
> rfatpol 1 2
> rfdir 1 1 1
> tolvrs 1.0d-8
> # non-spinor wavefunctions, without SO coupling
>  nband   5
> #Common data
>  acell 3*4.5672  Angstroms
>  angdeg 60 60 60
>  chkprim 0
>  ecut  30
>  natom  2
>  ntypat  2
>  typat  1 2
>  xred    3*0.0d0
>          3*0.5d0
>  znucl 82 52
> #Kpt grid
> ngkpt 3*4
> nshiftk 4
> shiftk 0.5 0.5 0.5
>        0.5 0   0
>        0   0.5 0
>        0   0   0.5
> #SCF
>  iscf  5
>  diemac 10
>  nstep    100
>
>
> ######anaddb  input file#########################
> !Flags
>  dieflag   1     ! Frequency-dependent Dielectric tensor flag
>  ifcflag   1     ! Interatomic force constant flag
>  thmflag   1     ! Thermodynamical properties flag
> !Wavevector grid number 1 (coarse grid, from DDB)
>   brav    1      ! Bravais Lattice : 1-S.C., 2-F.C., 3-B.C., 4-Hex.)
>   ngqpt   4  4  4   ! 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
>   ifcana  1      ! Analysis of the IFCs
>   ifcout 16      ! Number of IFC's written in the output, per atom
>   natifc  2      ! Number of atoms in the cell for which ifc's are
> analysed
>    atifc  1 2    ! List of atoms
> !Phonon band structure output for band2eps - See note near end for
> ! dealing with gamma LO-TO splitting issue.
>    eivec  4
>    prtdos 1
> !Wavevector list number 1 (Reduced coordinates and normalization factor)
>   nph1l    41      ! number of phonons in list 1
>   qph1l   0.5000  0.5000  0.5000   1.0    !(L point)
>           0.5500  0.5500  0.5500   1.0
>           0.6000  0.6000  0.6000   1.0
>           0.6500  0.6500  0.6500   1.0
>           0.7000  0.7000  0.7000   1.0
>           0.7500  0.7500  0.7500   1.0
>           0.8000  0.8000  0.8000   1.0
>           0.8500  0.8500  0.8500   1.0
>           0.9000  0.9000  0.9000   1.0
>           0.9500  0.9500  0.9500   1.0
>           1.0000  1.0000  1.0000   1.0    !(gamma point)
>           0.9500  0.9500  1.0000   1.0
>           0.9000  0.9000  1.0000   1.0
>           0.8500  0.8500  1.0000   1.0
>           0.8000  0.8000  1.0000   1.0
>           0.7500  0.7500  1.0000   1.0
>           0.7000  0.7000  1.0000   1.0
>           0.6500  0.6500  1.0000   1.0
>           0.6000  0.6000  1.0000   1.0
>           0.5500  0.5500  1.0000   1.0
>           0.5000  0.5000  1.0000   1.0    !(X point)
>           0.4875  0.4875  0.9750   1.0
>           0.4750  0.4750  0.9500   1.0
>           0.4625  0.4625  0.9250   1.0
>           0.4500  0.4500  0.9000   1.0
>           0.4375  0.4375  0.8750   1.0
>           0.4250  0.4250  0.8500   1.0
>           0.4125  0.4125  0.8250   1.0
>           0.4000  0.4000  0.8000   1.0
>           0.3875  0.3875  0.7750   1.0
>           0.3750  0.3750  0.7500   1.0    !(K point)
>           0.3375  0.3375  0.6750   1.0
>           0.3000  0.3000  0.6000   1.0
>           0.2625  0.2625  0.5250   1.0
>           0.2250  0.2250  0.4500   1.0
>           0.1875  0.1875  0.3750   1.0
>           0.1500  0.1500  0.3000   1.0
>           0.1125  0.1125  0.2250   1.0
>           0.0750  0.0750  0.1500   1.0
>           0.0375  0.0375  0.0750   1.0
>           0.0000  0.0000  0.0000   1.0    !(gamma point)
>
> !Wavevector list number 2 (Cartesian directions for non-analytic gamma
> phonons)
>   nph2l    1       ! number of directions in list 2
>   qph2l   1.0  0.0  0.0    0.0
> !Wavevector grid number 2 (series of fine grids, extrapolated from interat
> forces)
>   ng2qpt   20 20 20  ! sample the BZ up to ngqpt2
>   ngrids   5         ! number of grids of increasing size
>   q2shft   3*0.0
> !Thermal information
>   nchan   1250   ! # of channels for the DOS with channel width 1 cm-1
>   nwchan  5      ! # of different channel widths from this integer down to
> 1 cm-1
>   thmtol  0.030  ! Tolerance on thermodynamical function fluctuations
>   ntemper 90     ! Number of temperatures
>   temperinc 2.  ! Increment of temperature in K for temperature
> dependency
>   tempermin 4.  ! Minimal temperature in Kelvin
> # This line added when defaults were changed (v5.3) to keep the previous,
> old behaviour
>   symdynmat 0
>