The ABINIT Users Mailing List ( CLOSED )

["Eric Bousquet" <Eric.Bousquet@ulg.ac.be>]

I Takeshi,

It seems that you didn't apply any acoustic sum rule.
Can you redo your calculations of phonons by including the acoustic sum
rule and let see the results?
Since from each different ecut you don't have exactly the same violation
of the acoustic sum rule (ideally the acoustic modes should have a
frequency of 0 cm-1), your frequencies and eigenvectors will be affected
differently on each ecut.

Regards,

Eric


> Dear Prof. Gonze and all,
>
>> Please, see Philippe Ghosez's thesis, precisely on BaTiO3 :
>> http://www.phythema.ulg.ac.be/Download/download.php
>> You will find interesting information about the cut-off energy
>> convergence in an appendix
>> of this thesis.
>
> Thank you for your advice. I took a look in that very
> nice thesis and found that Teter's pseudopotentials
> were in use. But the pseudopotential for oxygen
> (r_c = 1.65) was softer than 8o.phoney.mod (r_c = 1.49).
>
> Here, I picked up three eigenvalues [eV/Angstrom^2] of
> the force constant matrix at the Gamma point and listed
> their ecut [Hartree] dependence. Modes are the
> Gamma15 soft mode, the acoustic translational mode
> (Ideally, it should be zero.) and the Gamma25 mode.
>
> ecut Gamma15    Acoustic   Gamma25
> 35  -0.456122   0.195207   5.003634
> 40  -0.994634  -0.028809   4.869130
> 45  -0.400629   0.046698   4.906948
> 50  -0.616130   0.037663   4.925377
> 55  -0.638695   0.025415   4.917949
> 57  -0.652137   0.013472   4.910288
> 60  -0.644218   0.014311   4.912821
> 61  -0.643811   0.014193   4.912773
> 62  -0.642569   0.014140   4.912736
> 65  -0.656336   0.007038   4.910474
> 70  -0.685880   0.007253   4.908248
> 75  -0.685909   0.007671   4.909921
> 80  -0.648047   0.008204   4.911302
>
>
> Frozen-phonon calculation with ecut=60:
> a0 =   3.9388898 [Angstrom]
> eigenvalues [eV/Angstrom^2] and eigenvectors of force_constant_matrix
> 1  -0.630966  -0.2163  -0.7518   0.2721   0.2721   0.4899
> 2   0.014762   0.4549   0.4690   0.4393   0.4393   0.4327
> 3   4.913130   0.0000   0.0000   0.7071  -0.7071   0.0000
> 4   9.570920   0.8536  -0.4055  -0.2310  -0.2310   0.0112
> 5  14.546354  -0.1327   0.2245  -0.4239  -0.4239   0.7568
> (Just for reference, input files are attached to this mail.)
>
>
> And, here is the ecut dependence of phonon frequency in
> [cm^-1] unit (The LO-TO splittings are not included.).
> I have done
> pwd ; grep -A 8 '  Phonon wavevector' perovskite-Gamma.out | grep '^-'
> in each directory.
>
> /BaTiO3-phonon-24-a0-3.940-8x8x8-ecut35-5.6.4
> - -7.058621E+01 -7.058621E+01 -7.058388E+01  3.066612E+01  3.066721E+01
> -  3.066721E+01  1.905540E+02  1.905544E+02  1.905544E+02  2.916225E+02
> -  2.916225E+02  2.916225E+02  4.911043E+02  4.911045E+02  4.911045E+02
> /BaTiO3-phonon-17-abinitio-a0-8x8x8-ecut40-5.6.4/force-constant-matrix
> - -9.439416E+01 -9.439416E+01 -9.439344E+01 -1.322782E+01 -1.322782E+01
> - -1.322750E+01  1.854138E+02  1.854140E+02  1.854140E+02  2.876762E+02
> -  2.876762E+02  2.876762E+02  4.889197E+02  4.889198E+02  4.889198E+02
> /BaTiO3-phonon-22-a0-3.940-8x8x8-ecut45-5.6.4
> - -6.368055E+01 -6.367916E+01 -6.367916E+01  1.575238E+01  1.575238E+01
> -  1.575554E+01  1.873933E+02  1.873933E+02  1.873935E+02  2.887912E+02
> -  2.887912E+02  2.887912E+02  4.907777E+02  4.907777E+02  4.907777E+02
> /BaTiO3-phonon-23-a0-3.940-8x8x8-ecut50-5.6.4
> - -7.754560E+01 -7.754560E+01 -7.754443E+01  1.441634E+01  1.441634E+01
> -  1.441651E+01  1.871320E+02  1.871322E+02  1.871322E+02  2.893330E+02
> -  2.893330E+02  2.893330E+02  4.904599E+02  4.904600E+02  4.904600E+02
> /BaTiO3-phonon-26-a0-3.940-8x8x8-ecut55-5.6.4
> - -7.839328E+01 -7.839328E+01 -7.838663E+01  1.193403E+01  1.193621E+01
> -  1.193621E+01  1.869438E+02  1.869441E+02  1.869441E+02  2.891148E+02
> -  2.891148E+02  2.891148E+02  4.900809E+02  4.900818E+02  4.900818E+02
> /BaTiO3-phonon-26-a0-3.940-8x8x8-ecut55-5.6.4
> - -7.839328E+01 -7.839328E+01 -7.838663E+01  1.193403E+01  1.193621E+01
> -  1.193621E+01  1.869438E+02  1.869441E+02  1.869441E+02  2.891148E+02
> -  2.891148E+02  2.891148E+02  4.900809E+02  4.900818E+02  4.900818E+02
> /BaTiO3-phonon-27-a0-3.940-8x8x8-Gamma-ecut-dep-5.6.4/ecut57
> - -7.873250E+01 -7.873250E+01 -7.873052E+01  8.751815E+00  8.759139E+00
> -  8.759139E+00  1.866568E+02  1.866574E+02  1.866574E+02  2.888895E+02
> -  2.888895E+02  2.888895E+02  4.900179E+02  4.900179E+02  4.900179E+02
> /BaTiO3-phonon-27-a0-3.940-8x8x8-Gamma-ecut-dep-5.6.4/ecut60
> - -7.824132E+01 -7.824132E+01 -7.823997E+01  9.019223E+00  9.021527E+00
> -  9.021527E+00  1.866891E+02  1.866893E+02  1.866893E+02  2.889640E+02
> -  2.889640E+02  2.889640E+02  4.900738E+02  4.900739E+02  4.900739E+02
> /BaTiO3-phonon-27-a0-3.940-8x8x8-Gamma-ecut-dep-5.6.4/ecut61
> - -7.821165E+01 -7.821165E+01 -7.820821E+01  8.985857E+00  8.986975E+00
> -  8.986975E+00  1.866876E+02  1.866880E+02  1.866880E+02  2.889626E+02
> -  2.889626E+02  2.889626E+02  4.900728E+02  4.900732E+02  4.900732E+02
> /BaTiO3-phonon-27-a0-3.940-8x8x8-Gamma-ecut-dep-5.6.4/ecut62
> - -7.813268E+01 -7.813268E+01 -7.813056E+01  8.964342E+00  8.966948E+00
> -  8.966948E+00  1.866836E+02  1.866838E+02  1.866838E+02  2.889615E+02
> -  2.889615E+02  2.889615E+02  4.900803E+02  4.900805E+02  4.900805E+02
> /BaTiO3-phonon-27-a0-3.940-8x8x8-Gamma-ecut-dep-5.6.4/ecut65
> - -7.858113E+01 -7.858037E+01 -7.858037E+01  6.359724E+00  6.359724E+00
> -  6.362257E+00  1.865175E+02  1.865175E+02  1.865175E+02  2.888950E+02
> -  2.888950E+02  2.888950E+02  4.900551E+02  4.900551E+02  4.900551E+02
> /BaTiO3-phonon-27-a0-3.940-8x8x8-Gamma-ecut-dep-5.6.4/ecut70
> - -8.031784E+01 -8.031746E+01 -8.031746E+01  6.454205E+00  6.454205E+00
> -  6.456866E+00  1.865108E+02  1.865108E+02  1.865110E+02  2.888295E+02
> -  2.888295E+02  2.888295E+02  4.898023E+02  4.898024E+02  4.898024E+02
> /BaTiO3-phonon-27-a0-3.940-8x8x8-Gamma-ecut-dep-5.6.4/ecut75
> - -8.035355E+01 -8.035317E+01 -8.035317E+01  6.635282E+00  6.635282E+00
> -  6.637831E+00  1.864521E+02  1.864521E+02  1.864522E+02  2.888787E+02
> -  2.888787E+02  2.888787E+02  4.899633E+02  4.899633E+02  4.899633E+02
> /BaTiO3-phonon-27-a0-3.940-8x8x8-Gamma-ecut-dep-5.6.4/ecut80
> - -7.816902E+01 -7.816902E+01 -7.816585E+01  6.855128E+00  6.855128E+00
> -  6.858712E+00  1.865275E+02  1.865275E+02  1.865275E+02  2.889193E+02
> -  2.889193E+02  2.889193E+02  4.901485E+02  4.901490E+02  4.901490E+02
>
>
> I conclude that I can safely use ecut=60, maybe...
>
>
> Thank you again,
> -- Takeshi Nishimatsu
>
>
>


Universite de Liege
Institut de Physique, Bat. B5
Allee du 6 aout, 17
B-4000 Sart Tilman
BELGIUM

Phone : ++(32) (0)4-366.37.22
Fax   : ++(32) (0)4-366.36.29

http://www.ulg.ac.be/phythema