something wrong with the phonon caused imaginary freq

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shaoziji
Posts: 16
Joined: Sat Jan 09, 2016 4:57 am

something wrong with the phonon caused imaginary freq

Post by shaoziji » Tue Mar 15, 2016 1:52 am

Dear users/developers,
I'm a new user of abinit and I am now doing the test an exercise, I want to repeat the previous work of H3S bcc cubic structure,the structure should be dynamical stability but when I calculated the phonon after geometry relaxation at 200 GPa , the phonon frequency at q point 0.5 0.5 0.5 was negative frequencies about -300 cm-1, and I cannot get rid of it , please help me to find the reason.
First I do the geometry relaxation :

Code: Select all

#Dataset of opt and occupation 
#=============================
occopt     6
tsmear     0.001 
optcell    2
ionmov     2
tolmxf     1.0d-14
ntime      1000000
dilatmx    2.00
ecutsm     0.5
strprecon  0.1
strtarget  -6.797858d-3  -6.797858d-3  -6.797858d-3  0  0  0
# Definition of the unit cell
#=============================
acell      3*4.8813129966E+00 
rprim      -0.5   0.5   0.5
            0.5  -0.5   0.5
            0.5   0.5  -0.5
#Definition of the atoms types
#=============================
ntypat     2
znucl      1 16
natom      4
typat      1 1 1 2
#tolvrs     1.0d-20
xred        5.00000000000000E-01  5.00000000000000E-01  0.00000000000000E+00
            0.00000000000000E+00  5.00000000000000E-01  5.00000000000000E-01
            5.00000000000000E-01  0.00000000000000E+00  5.00000000000000E-01
            0.00000000000000E+00  0.00000000000000E+00  0.00000000000000E+00 
#Definition of the k-point grid
#==========================================
kptopt     1
ngkpt      32 32 32
nshiftk    1

shiftk     0 0 0 

#Definition of the SCF procedure
#==========================================
#iscf        5
ecut        40 
nband       15
toldff      1.0d-15
#diemac 3.0
nstep       100000

#Definition of the outfile information
#==========================================
prtwf 0


and than I used the new acell to run the phonon freq for 3 perticular q points Gamma point 0 0 0 and point 0.25 0.25 0.25 and point 0.5 0.5 0.5

Code: Select all

# Crystalline AlAs : computation of the phonon spectrum

   ndtset  5
#Set 1 : ground state self-consistency
occopt 6
tsmear 0.001
  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   5.00000000E-01  5.00000000E-01  5.00000000E-01
     qpt5   2.50000000E-01  2.50000000E-01  2.50000000E-01

#Set 2 : Response function calculation of d/dk wave function
#
    iscf2   -3         # Need this non-self-consistent option for d/dk
  kptopt2   3          # Modify default to use time-reversal symmetry
  rfphon2   0          # Cancel default
  rfelfd2   2          # Calculate d/dk wave function only
  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   3          # 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 4        # Treat displacements of all atoms
    rfdir   1 1 1      # Do all directions (symmetry will be used)
   tolvrs   1.0d-18     # This default is active for sets 3-10

#######################################################################
#Common input variables

#Definition of the unit cell
    acell   3*4.8813129966E+00  This is equivalent to   10.61 10.61 10.61
    rprim   -0.5   0.5   0.5   # In lessons 1 and 2, these primitive vectors
             0.5  -0.5   0.5   # (to be scaled by acell) were 1 0 0  0 1 0  0 0 1
             0.5   0.5  -0.5   # that is, the default.

#Definition of the atom types
   ntypat   2         # There are two types of atom
    znucl   1 16     # 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   4         # There are two atoms
    typat   1 1 1 2       # The first is of type 1 (Al), the second is of type 2 (As).
                       
     xred   5.0000000000E-01  5.0000000000E-01  0.0000000000E+00
            0.0000000000E+00  5.0000000000E-01  5.0000000000E-01
            5.0000000000E-01  0.0000000000E+00  5.0000000000E-01
            0.0000000000E+00  0.0000000000E+00  0.0000000000E+00
             

#Gives the number of band, explicitely (do not take the default)
    nband   15         

#Exchange-correlation functional

  #    ixc   1             # LDA Teter Pade parametrization

#Definition of the planewave basis set

     ecut   40           # Maximal kinetic energy cut-off, in Hartree

#Definition of the k-point grid
    ngkpt   24  24  24         
  nshiftk   1              # Use one copy of grid only (default)
   shiftk   0.0 0.0 0.0    # This gives the usual fcc Monkhorst-Pack grid
           
           
           

#Definition of the SCF procedure
     iscf   7          # Self-consistent calculation, using algorithm 5
    nstep   100000         # Maximal number of SCF cycles
  # diemac   9.0        # Although this is not mandatory, it is worth to
                       # precondition the SCF cycle. The model dielectric
                       # function used as the standard preconditioner
                       # is described in the "dielng" input variable section.
                       # The dielectric constant of AlAs is smaller that the one of Si (=12).
# add to conserve old < 6.7.2 behavior for calculating forces at each SCF step
 optforces 1


#%%<BEGIN TEST_INFO>
#%% [setup]
#%% executable = abinit
#%% test_chain = trf2_1.in, trf2_3.in, trf2_4.in, trf2_5.in, trf2_6.in, trf2_7.in
#%% [files]
#%% files_to_test =
#%%   trf2_1.out, tolnlines= 14, tolabs=  5.000e-05, tolrel=  5.000e-04, fld_options=-medium
#%% psp_files =  13al.981214.fhi, 33as.pspnc
#%% [paral_info]
#%% max_nprocs = 2
#%% [extra_info]
#%% authors =
#%% keywords = NC, DFPT
#%% description =
#%%<END TEST_INFO>


I got imaginary freq at 0.5 0.5 0.5 about -300 cm -1 and I really don't know what to do
Thank you very much

ilukacevic
Posts: 271
Joined: Sat Jan 16, 2010 12:05 pm
Location: Dept. of Physics, University J. J. Strossmayer, Osijek, Croatia
Contact:

Re: something wrong with the phonon caused imaginary freq

Post by ilukacevic » Tue Mar 15, 2016 8:41 am

Hi!

1] Before anything else, you have to make sure that all common variables have the same values in both calculations. And I can see that some of them do not, like ngkpt, etc. Also it is advised to use the same energy tolerance criterion, while you use toldff in the relaxation and tolvrs in RF. Because of that, in your RF calculation, you are probably not obtaining the WF and density corresponding to the relaxed geometry, which might lead to an unstable phonon mode.

2] What is the value of pressure in the end of your relaxation and in the end of your RF 1st dataset? They would have to be exactly the same.

Best regards,

Igor

shaoziji
Posts: 16
Joined: Sat Jan 09, 2016 4:57 am

Re: something wrong with the phonon caused imaginary freq

Post by shaoziji » Wed Mar 16, 2016 12:38 pm

ilukacevic wrote:Hi!

1] Before anything else, you have to make sure that all common variables have the same values in both calculations. And I can see that some of them do not, like ngkpt, etc. Also it is advised to use the same energy tolerance criterion, while you use toldff in the relaxation and tolvrs in RF. Because of that, in your RF calculation, you are probably not obtaining the WF and density corresponding to the relaxed geometry, which might lead to an unstable phonon mode.

2] What is the value of pressure in the end of your relaxation and in the end of your RF 1st dataset? They would have to be exactly the same.

Best regards,

Igor

Dear Igor,

Thank you so much for your apply, I tried to fixed my Input as you suggested, I used tolvrs = 1.0 d -18 and same ngkpt 32 32 32 in both relaxation and RF. but the phonon freq is sill negative around - 300 cm -1 , the pressure ( stress tensor Pa ) at the end of my relaxation is 200 GPa ( I set it at the relaxation ) but the end of RF 1st dataset (scf) is 746.05 GPa even I add the dilatmx, ecutsm, strprecon and strtarget as same as the relaxation at the 1st step of RF.

Sincerely thanks

Shao

shaoziji
Posts: 16
Joined: Sat Jan 09, 2016 4:57 am

Re: something wrong with the phonon caused imaginary freq

Post by shaoziji » Wed Mar 16, 2016 12:38 pm

ilukacevic wrote:Hi!

1] Before anything else, you have to make sure that all common variables have the same values in both calculations. And I can see that some of them do not, like ngkpt, etc. Also it is advised to use the same energy tolerance criterion, while you use toldff in the relaxation and tolvrs in RF. Because of that, in your RF calculation, you are probably not obtaining the WF and density corresponding to the relaxed geometry, which might lead to an unstable phonon mode.

2] What is the value of pressure in the end of your relaxation and in the end of your RF 1st dataset? They would have to be exactly the same.

Best regards,

Igor

Dear Igor,

Thank you so much for your apply, I tried to fixed my Input as you suggested, I used tolvrs = 1.0 d -18 and same ngkpt 32 32 32 in both relaxation and RF. but the phonon freq is sill negative around - 300 cm -1 , the pressure ( stress tensor Pa ) at the end of my relaxation is 200 GPa ( I set it at the relaxation ) but the end of RF 1st dataset (scf) is 746.05 GPa even I add the dilatmx, ecutsm, strprecon and strtarget as same as the relaxation at the 1st step of RF.

Sincerely thanks

Shao

ilukacevic
Posts: 271
Joined: Sat Jan 16, 2010 12:05 pm
Location: Dept. of Physics, University J. J. Strossmayer, Osijek, Croatia
Contact:

Re: something wrong with the phonon caused imaginary freq

Post by ilukacevic » Wed Mar 16, 2016 12:56 pm

That might be the source of your problem.

Did you insert the relaxed acell into your RF input file? I see from the inputs your provided in your first post that the acell in the RF input file is the same as in the relaxation input file. If you used that RF input file, you should change acell.

Igor

shaoziji
Posts: 16
Joined: Sat Jan 09, 2016 4:57 am

Re: something wrong with the phonon caused imaginary freq

Post by shaoziji » Wed Mar 16, 2016 1:09 pm

ilukacevic wrote:That might be the source of your problem.

Did you insert the relaxed acell into your RF input file? I see from the inputs your provided in your first post that the acell in the RF input file is the same as in the relaxation input file. If you used that RF input file, you should change acell.

Igor

Yes, I copied the acell from the out file of the relaxation and paste it at the RF step, the Input file I post above is the second step of the relaxation because I did the ralzation two times in order to sure the acell would not change so the acell parameters of the out file and input file are the same. But I don't know why the pressures are different . Is that the crucial point for the negative freq ?

shaoziji
Posts: 16
Joined: Sat Jan 09, 2016 4:57 am

Re: something wrong with the phonon caused imaginary freq

Post by shaoziji » Wed Mar 16, 2016 1:09 pm

ilukacevic wrote:That might be the source of your problem.

Did you insert the relaxed acell into your RF input file? I see from the inputs your provided in your first post that the acell in the RF input file is the same as in the relaxation input file. If you used that RF input file, you should change acell.

Igor

Yes, I copied the acell from the out file of the relaxation and paste it at the RF step, the Input file I post above is the second step of the relaxation because I did the ralzation two times in order to sure the acell would not change so the acell parameters of the out file and input file are the same. But I don't know why the pressures are different . Is that the crucial point for the negative freq ?

ilukacevic
Posts: 271
Joined: Sat Jan 16, 2010 12:05 pm
Location: Dept. of Physics, University J. J. Strossmayer, Osijek, Croatia
Contact:

Re: something wrong with the phonon caused imaginary freq

Post by ilukacevic » Wed Mar 16, 2016 1:26 pm

Very much possible. It is known that in some systems phonon frequencies become imaginary at high pressures. You could have the same situation.

Try to solve first the problem of different pressures in relaxation and RF calculations. If all you input variables are the same, then you should get the same pressure. Since it is not the same, it means that not all of your input variables have the same values.

Igor

shaoziji
Posts: 16
Joined: Sat Jan 09, 2016 4:57 am

Re: something wrong with the phonon caused imaginary freq

Post by shaoziji » Thu Mar 17, 2016 5:45 am

ilukacevic wrote:Very much possible. It is known that in some systems phonon frequencies become imaginary at high pressures. You could have the same situation.

Try to solve first the problem of different pressures in relaxation and RF calculations. If all you input variables are the same, then you should get the same pressure. Since it is not the same, it means that not all of your input variables have the same values.

Igor

Dear Igor,

I redid the relaxation and RF but still not work,
For the relaxation the acell in input file was gotten from the relaxation result of VASP with the same GGA ex-interaction the tolerance was tolvrs = 1.0 d -18. The acell in the out file was used by the RF . The first step of the RF was scf and if I didn't open the optcell and ionmov, the pressure of the scf was always different from the 200 GPa I set in the relaxation step . But I open the optcell and ionmov as the relaxation (maybe it was not the scf but the relaxation), the 1st step's pressure was 200 GPa but the freq calculated with the wavefunction from the 1st step was more nagetive about - 400 cm -1 . I really don' t know what's wrong with it .

Code: Select all

occopt     6
tsmear     0.001 
optcell    2
ionmov     2
tolvrs     1.0d-18

ntime      1000000
dilatmx    2.00
ecutsm     0.5
strprecon  0.1
strtarget  -6.797858d-3  -6.797858d-3  -6.797858d-3  0  0  0 # 1 Ha/Bohr**3 = 29421.033 GPa
                                              # 1GPa = 3.4 E-5 atomic units
# Definition of the unit cell
#=============================
acell      3*2.58325 Angstrom 
rprim      -0.5   0.5   0.5
            0.5  -0.5   0.5
            0.5   0.5  -0.5

#Definition of the atoms types
#=============================
ntypat     2
znucl      1 16
natom      4
typat      1 1 1 2

xred        5.00000000000000E-01  5.00000000000000E-01  0.00000000000000E+00
            0.00000000000000E+00  5.00000000000000E-01  5.00000000000000E-01
            5.00000000000000E-01  0.00000000000000E+00  5.00000000000000E-01
            0.00000000000000E+00  0.00000000000000E+00  0.00000000000000E+00
#Definition of the k-point grid
#==========================================
kptopt     1
ngkpt      32 32 32 
nshiftk    1
 
shiftk     0 0 0


#Definition of the SCF procedure
#==========================================
iscf        7
ecut        40 
nband       15
#toldff      1.0d-15
#diemac 3.0
nstep       100000
 
#Definition of the outfile information
#==========================================
prtwf 0

shaoziji
Posts: 16
Joined: Sat Jan 09, 2016 4:57 am

Re: something wrong with the phonon caused imaginary freq

Post by shaoziji » Thu Mar 17, 2016 5:55 am

shaoziji wrote:
ilukacevic wrote:Very much possible. It is known that in some systems phonon frequencies become imaginary at high pressures. You could have the same situation.

Try to solve first the problem of different pressures in relaxation and RF calculations. If all you input variables are the same, then you should get the same pressure. Since it is not the same, it means that not all of your input variables have the same values.

Igor

Dear Igor,

I redid the relaxation and RF but still not work,
For the relaxation the acell in input file was gotten from the relaxation result of VASP with the same GGA ex-interaction the tolerance was tolvrs = 1.0 d -18. The acell in the out file was used by the RF . The first step of the RF was scf and if I didn't open the optcell and ionmov, the pressure of the scf was always different from the 200 GPa I set in the relaxation step . But I open the optcell and ionmov as the relaxation (maybe it was not the scf but the relaxation), the 1st step's pressure was 200 GPa but the freq calculated with the wavefunction from the 1st step was more nagetive about - 400 cm -1 . I really don' t know what's wrong with it .

Code: Select all

occopt     6
tsmear     0.001 
optcell    2
ionmov     2
tolvrs     1.0d-18

ntime      1000000
dilatmx    2.00
ecutsm     0.5
strprecon  0.1
strtarget  -6.797858d-3  -6.797858d-3  -6.797858d-3  0  0  0 # 1 Ha/Bohr**3 = 29421.033 GPa
                                              # 1GPa = 3.4 E-5 atomic units
# Definition of the unit cell
#=============================
acell      3*2.58325 Angstrom 
rprim      -0.5   0.5   0.5
            0.5  -0.5   0.5
            0.5   0.5  -0.5

#Definition of the atoms types
#=============================
ntypat     2
znucl      1 16
natom      4
typat      1 1 1 2

xred        5.00000000000000E-01  5.00000000000000E-01  0.00000000000000E+00
            0.00000000000000E+00  5.00000000000000E-01  5.00000000000000E-01
            5.00000000000000E-01  0.00000000000000E+00  5.00000000000000E-01
            0.00000000000000E+00  0.00000000000000E+00  0.00000000000000E+00
#Definition of the k-point grid
#==========================================
kptopt     1
ngkpt      32 32 32 
nshiftk    1
 
shiftk     0 0 0


#Definition of the SCF procedure
#==========================================
iscf        7
ecut        40 
nband       15
#toldff      1.0d-15
#diemac 3.0
nstep       100000
 
#Definition of the outfile information
#==========================================
prtwf 0

and the RF input file is
scf in 1st step

Code: Select all

# Crystalline AlAs : computation of the phonon spectrum

   ndtset  5
#Set 1 : ground state self-consistency
occopt 6
tsmear 0.001
  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
 dilatmx1    2.00
ecutsm1     0.5
strprecon1  0.1
strtarget1  -6.797858d-3  -6.797858d-3  -6.797858d-3  0  0  0
#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   5.00000000E-01  5.00000000E-01  5.00000000E-01
     qpt5   2.50000000E-01  2.50000000E-01  2.50000000E-01

#Set 2 : Response function calculation of d/dk wave function

    iscf2   -3         # Need this non-self-consistent option for d/dk
  kptopt2   3          # Modify default to use time-reversal symmetry
  rfphon2   0          # Cancel default
  rfelfd2   2          # Calculate d/dk wave function only
  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   3          # 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 4        # Treat displacements of all atoms
    rfdir   1 1 1      # Do all directions (symmetry will be used)
   tolvrs   1.0d-18     # This default is active for sets 3-10

#######################################################################
#Common input variables

#Definition of the unit cell
    acell   3*4.8819240377E+00 #4.8813129966E+00 # This is equivalent to   10.61 10.61 10.61
    rprim   -0.5   0.5   0.5   # In lessons 1 and 2, these primitive vectors
             0.5  -0.5   0.5   # (to be scaled by acell) were 1 0 0  0 1 0  0 0 1
             0.5   0.5  -0.5   # that is, the default.

#Definition of the atom types
   ntypat   2         # There are two types of atom
    znucl   1 16     # 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   4         # There are two atoms
    typat   1 1 1 2       # The first is of type 1 (Al), the second is of type 2 (As).
                       
     xred   5.0000000000E-01  5.0000000000E-01  0.0000000000E+00
            0.0000000000E+00  5.0000000000E-01  5.0000000000E-01
            5.0000000000E-01  0.0000000000E+00  5.0000000000E-01
            0.0000000000E+00  0.0000000000E+00  0.0000000000E+00
             

#Gives the number of band, explicitely (do not take the default)
    nband   15         

#Exchange-correlation functional

  #    ixc   1             # LDA Teter Pade parametrization

#Definition of the planewave basis set

     ecut   40           # Maximal kinetic energy cut-off, in Hartree

#Definition of the k-point grid
    ngkpt   32  32  32         
  nshiftk   1              # Use one copy of grid only (default)
   shiftk   0.0 0.0 0.0    # This gives the usual fcc Monkhorst-Pack grid
           
           
           

#Definition of the SCF procedure
     iscf   7          # Self-consistent calculation, using algorithm 5
    nstep   100000         # Maximal number of SCF cycles
  # diemac   9.0        # Although this is not mandatory, it is worth to
                       # precondition the SCF cycle. The model dielectric
                       # function used as the standard preconditioner
                       # is described in the "dielng" input variable section.
                       # The dielectric constant of AlAs is smaller that the one of Si (=12).
# add to conserve old < 6.7.2 behavior for calculating forces at each SCF step
 optforces 1


#%%<BEGIN TEST_INFO>
#%% [setup]
#%% executable = abinit
#%% test_chain = trf2_1.in, trf2_3.in, trf2_4.in, trf2_5.in, trf2_6.in, trf2_7.in
#%% [files]
#%% files_to_test =
#%%   trf2_1.out, tolnlines= 14, tolabs=  5.000e-05, tolrel=  5.000e-04, fld_options=-medium
#%% psp_files =  13al.981214.fhi, 33as.pspnc
#%% [paral_info]
#%% max_nprocs = 2
#%% [extra_info]
#%% authors =
#%% keywords = NC, DFPT
#%% description =
#%%<END TEST_INFO>


and I did another RF calculation to make the ralaxation as the fist step only added the optcell = 2 , ionmov = 2 and ntime = 10000

I don' t know how to show you my log file because it is too long .

Sincerely thank you

Shao

ilukacevic
Posts: 271
Joined: Sat Jan 16, 2010 12:05 pm
Location: Dept. of Physics, University J. J. Strossmayer, Osijek, Croatia
Contact:

Re: something wrong with the phonon caused imaginary freq

Post by ilukacevic » Thu Mar 17, 2016 9:42 am

If you obtained the required pressure at the end of the 1st dataset of your RF calculation, then you are using the correct wavefunction. But since your frequencies are still negative, it means that there is a physical problem in the simulated system taking into account the used approximations (xc, psudopotential characteristics, etc).

Oh, just to make sure, are you reading the wavefunction from the correct dataset in your RF calculation?

Igor

shaoziji
Posts: 16
Joined: Sat Jan 09, 2016 4:57 am

Re: something wrong with the phonon caused imaginary freq

Post by shaoziji » Sat Mar 26, 2016 5:00 am

ilukacevic wrote:If you obtained the required pressure at the end of the 1st dataset of your RF calculation, then you are using the correct wavefunction. But since your frequencies are still negative, it means that there is a physical problem in the simulated system taking into account the used approximations (xc, psudopotential characteristics, etc).

Oh, just to make sure, are you reading the wavefunction from the correct dataset in your RF calculation?

Igor

Dear Igor,
I recalculated the whole things and I finally found my fault, I forgot to change the rprim after the relaxition and I changed the rprim of the RF calculation by the relaxed one and the negative freq disappeared. That's my fault and I'm terribly sorry for causing you so much of time. But I had a new confusion about the calculation of phonon, I just ues the example trf2_5.in to get the band data of phonon but the speed of the calcluation was too slow . Is the speed a normal phenomenon ?

Code: Select all

!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    3      ! 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

!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   101      ! number of phonons in list 1                             

  qph1l   0.000000  0.000000  0.000000  1.00    !(gamma point)
          0.025000 -0.025000  0.025000  1.00
          0.050000 -0.050000  0.050000  1.00
          0.075000 -0.075000  0.075000  1.00
          0.100000 -0.100000  0.100000  1.00
          0.125000 -0.125000  0.125000  1.00
          0.150000 -0.150000  0.150000  1.00
          0.175000 -0.175000  0.175000  1.00
          0.200000 -0.200000  0.200000  1.00
          0.225000 -0.225000  0.225000  1.00
          0.250000 -0.250000  0.250000  1.00
          0.275000 -0.275000  0.275000  1.00
          0.300000 -0.300000  0.300000  1.00
          0.325000 -0.325000  0.325000  1.00
          0.350000 -0.350000  0.350000  1.00
          0.375000 -0.375000  0.375000  1.00
          0.400000 -0.400000  0.400000  1.00
          0.425000 -0.425000  0.425000  1.00
          0.450000 -0.450000  0.450000  1.00
          0.475000 -0.475000  0.475000  1.00
          0.500000 -0.500000  0.500000  1.00
          0.475000 -0.475000  0.500000  1.00
          0.450000 -0.450000  0.500000  1.00
          0.425000 -0.425000  0.500000  1.00
          0.400000 -0.400000  0.500000  1.00
          0.375000 -0.375000  0.500000  1.00
          0.350000 -0.350000  0.500000  1.00
          0.325000 -0.325000  0.500000  1.00
          0.300000 -0.300000  0.500000  1.00
          0.275000 -0.275000  0.500000  1.00
          0.250000 -0.250000  0.500000  1.00
          0.225000 -0.225000  0.500000  1.00
          0.200000 -0.200000  0.500000  1.00
          0.175000 -0.175000  0.500000  1.00
          0.150000 -0.150000  0.500000  1.00
          0.125000 -0.125000  0.500000  1.00
          0.100000 -0.100000  0.500000  1.00
          0.075000 -0.075000  0.500000  1.00
          0.050000 -0.050000  0.500000  1.00
          0.025000 -0.025000  0.500000  1.00
         -0.000000  0.000000  0.500000  1.00
          0.012500  0.012500  0.487500  1.00
          0.025000  0.025000  0.475000  1.00
          0.037500  0.037500  0.462500  1.00
          0.050000  0.050000  0.450000  1.00
          0.062500  0.062500  0.437500  1.00
          0.075000  0.075000  0.425000  1.00
          0.087500  0.087500  0.412500  1.00
          0.100000  0.100000  0.400000  1.00
          0.112500  0.112500  0.387500  1.00
          0.125000  0.125000  0.375000  1.00
          0.137500  0.137500  0.362500  1.00
          0.150000  0.150000  0.350000  1.00
          0.162500  0.162500  0.337500  1.00
          0.175000  0.175000  0.325000  1.00
          0.187500  0.187500  0.312500  1.00
          0.200000  0.200000  0.300000  1.00
          0.212500  0.212500  0.287500  1.00
          0.225000  0.225000  0.275000  1.00
          0.237500  0.237500  0.262500  1.00
          0.250000  0.250000  0.250000  1.00
          0.237500  0.237500  0.237500  1.00
          0.225000  0.225000  0.225000  1.00
          0.212500  0.212500  0.212500  1.00
          0.200000  0.200000  0.200000  1.00
          0.187500  0.187500  0.187500  1.00
          0.175000  0.175000  0.175000  1.00
          0.162500  0.162500  0.162500  1.00
          0.150000  0.150000  0.150000  1.00
          0.137500  0.137500  0.137500  1.00
          0.125000  0.125000  0.125000  1.00
          0.112500  0.112500  0.112500  1.00
          0.100000  0.100000  0.100000  1.00
          0.087500  0.087500  0.087500  1.00
          0.075000  0.075000  0.075000  1.00
          0.062500  0.062500  0.062500  1.00
          0.050000  0.050000  0.050000  1.00
          0.037500  0.037500  0.037500  1.00
          0.025000  0.025000  0.025000  1.00
          0.012500  0.012500  0.012500  1.00
         -0.000000  0.000000 -0.000000  1.00
         -0.000000  0.000000  0.025000  1.00
         -0.000000  0.000000  0.050000  1.00
         -0.000000  0.000000  0.075000  1.00
         -0.000000  0.000000  0.100000  1.00
         -0.000000  0.000000  0.125000  1.00
         -0.000000  0.000000  0.150000  1.00
         -0.000000  0.000000  0.175000  1.00
         -0.000000  0.000000  0.200000  1.00
         -0.000000  0.000000  0.225000  1.00
         -0.000000  0.000000  0.250000  1.00
         -0.000000  0.000000  0.275000  1.00
         -0.000000  0.000000  0.300000  1.00
         -0.000000  0.000000  0.325000  1.00
         -0.000000  0.000000  0.350000  1.00
         -0.000000  0.000000  0.375000  1.00
         -0.000000  0.000000  0.400000  1.00
         -0.000000  0.000000  0.425000  1.00
         -0.000000  0.000000  0.450000  1.00
         -0.000000  0.000000  0.475000  1.00
         -0.000000  0.000000  0.500000  1.00
!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


#%%<BEGIN TEST_INFO>
#%% [setup]
#%% executable = anaddb
#%% test_chain = trf2_1.in, trf2_3.in, trf2_4.in, trf2_5.in, trf2_6.in, trf2_7.in
#%% input_ddb = trf2_3.ddb.out
#%% [files]
#%% files_to_test =
#%%   trf2_5.out, tolnlines=  0, tolabs=  0.000e+00, tolrel=  0.000e+00, fld_options=-easy
#%% psp_files =  13al.981214.fhi, 33as.pspnc
#%% [paral_info]
#%% max_nprocs = 1
#%% [extra_info]
#%% authors =
#%% keywords =
#%% description =
#%%<END TEST_INFO>

Thank you very much

Shao

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