[Q-e-developers] Probable bug in phonons
stefano de gironcoli
degironc at sissa.it
Sat Nov 29 12:36:26 CET 2014
Dear Daniele, Giovanni,
the phonon corresponding to commensurate q-points are conceptually
equivalent to a Gamma calculation in a supercell.
As such the equations involved have a well defined expression that
one could connect to a "frozen phonon" calculation with physical meaning.
Phonons for q-points that are not commensurate are strictly
speacking impossible to describe on a supercell so they are "unphysical"
and one relies on a continuity argument to believe that the same
formulas away from commensurate points give a smooth dispersion. In the
early days I tested this continuity for semiconductors and simple metals
but things have evolved a lot since and i don't know how much this fact
has been monitored.
Somehow the calculations you are performing challenge this
continuity argument
I would try to isolate the problem by performing similar
calculations with 1) a norm-conserving pseudopotential 2) with/without
nonlinear core correction 3) an uspp that requires significantly less
cutoff (like 30-180).
stefano
On 11/28/2014 02:33 PM, Giovanni Pizzi wrote:
> Dear QE developers,
>
> we have been working with 'simple' ferromagnetic bcc iron and were
> trying to calculate phonon dispersion with ph.x (5.1 QE version) on
> different q meshes at the theoretical electronic equilibrium volume
> and 'well' converged input parameters. Playing with the mesh of q
> points we have noticed the following:
>
> *Apparently, the frequencies calculated at q points that do not belong
> to the k-mesh of the underlying scf calculation are either negative or
> apparently 'random'.*
>
> On the other hand, q points belonging to the k-mesh display expected
> reasonable values. This means that using a q-mesh fully included in
> the k-mesh, you are able to get reasonable phonon dispersions
> comparable with experiments and you do not notice the problem.
>
> Trying to rationalize a bit more the problem, we have noticed that
> this behavior can be systematically reproduced with different svn
> versions of QE, back at least to revision 8500 and probably also
> before (we tested versions from 8500 to 11000 at steps of 500, and all
> provided the same "wrong" results, see data below). The test can be
> reproduced in reasonably short time with the input files reported at
> the end of this email (with pslibrary pseudos).
>
> We also provide in attachment an example of this behavior for the well
> converged calculations of Fe (input&outputs of pw and ph;
> kmesh=24x24x24, and phonons on 6x6x6 and 10x10x10 meshes).
> The attached figures show an example of the problem when the q-points
> are chosen along the (0,0,z) line, and a comparison between the
> "correct" interpolation for the 6x6x6 q-mesh (note that all phonons
> are positive) and the wrong interpolation for the 10x10x10 q-mesh.
>
> We wonder if someone else has ever experienced such a problem. We also
> think that this might be considered a severe problem that should be
> addressed especially because no error or warning message is provided.
>
> Thank you in advance,
>
> Daniele Dragoni and Giovanni Pizzi
>
>
>
>
> Data from older revisions:
> (folder name: SVN revision; the 8 qpoints belong to a 4x4x4 mesh, and
> only qpoints 1,3,8 are also in the 6x6x6 kmesh used for the SCF
> calculation; input files for SCF and PH follow below)
> 8500/dynmat1: omega( 1) = -0.590377 [THz] = -19.692841 [cm-1]
> 8500/dynmat1: omega( 2) = -0.590377 [THz] = -19.692841 [cm-1]
> 8500/dynmat1: omega( 3) = -0.590377 [THz] = -19.692841 [cm-1]
> 8500/dynmat2: omega( 1) = -18.238132 [THz] = -608.358600 [cm-1]
> 8500/dynmat2: omega( 2) = -14.917870 [THz] = -497.606579 [cm-1]
> 8500/dynmat2: omega( 3) = -5.360682 [THz] = -178.813111 [cm-1]
> 8500/dynmat3: omega( 1) = 5.116020 [THz] = 170.652049 [cm-1]
> 8500/dynmat3: omega( 2) = 6.910189 [THz] = 230.499104 [cm-1]
> 8500/dynmat3: omega( 3) = 9.840192 [THz] = 328.233473 [cm-1]
> 8500/dynmat4: omega( 1) = -17.878328 [THz] = -596.356827 [cm-1]
> 8500/dynmat4: omega( 2) = -14.055078 [THz] = -468.826953 [cm-1]
> 8500/dynmat4: omega( 3) = 4.075287 [THz] = 135.936946 [cm-1]
> 8500/dynmat5: omega( 1) = -20.413217 [THz] = -680.911617 [cm-1]
> 8500/dynmat5: omega( 2) = -20.309404 [THz] = -677.448788 [cm-1]
> 8500/dynmat5: omega( 3) = -20.309404 [THz] = -677.448788 [cm-1]
> 8500/dynmat6: omega( 1) = -18.153438 [THz] = -605.533512 [cm-1]
> 8500/dynmat6: omega( 2) = -13.491302 [THz] = -450.021393 [cm-1]
> 8500/dynmat6: omega( 3) = 7.301284 [THz] = 243.544619 [cm-1]
> 8500/dynmat7: omega( 1) = -19.842645 [THz] = -661.879388 [cm-1]
> 8500/dynmat7: omega( 2) = -19.842645 [THz] = -661.879388 [cm-1]
> 8500/dynmat7: omega( 3) = -19.842645 [THz] = -661.879388 [cm-1]
> 8500/dynmat8: omega( 1) = 10.185086 [THz] = 339.737896 [cm-1]
> 8500/dynmat8: omega( 2) = 10.185086 [THz] = 339.737896 [cm-1]
> 8500/dynmat8: omega( 3) = 10.185086 [THz] = 339.737896 [cm-1]
> 9000/dynmat1: omega( 1) = -0.592712 [THz] = -19.770745 [cm-1]
> 9000/dynmat1: omega( 2) = -0.592712 [THz] = -19.770745 [cm-1]
> 9000/dynmat1: omega( 3) = -0.592712 [THz] = -19.770745 [cm-1]
> 9000/dynmat2: omega( 1) = -18.237125 [THz] = -608.324994 [cm-1]
> 9000/dynmat2: omega( 2) = -14.916639 [THz] = -497.565517 [cm-1]
> 9000/dynmat2: omega( 3) = -5.358705 [THz] = -178.747149 [cm-1]
> 9000/dynmat3: omega( 1) = 5.117581 [THz] = 170.704131 [cm-1]
> 9000/dynmat3: omega( 2) = 6.911330 [THz] = 230.537139 [cm-1]
> 9000/dynmat3: omega( 3) = 9.841556 [THz] = 328.278961 [cm-1]
> 9000/dynmat4: omega( 1) = -17.877269 [THz] = -596.321499 [cm-1]
> 9000/dynmat4: omega( 2) = -14.053790 [THz] = -468.783972 [cm-1]
> 9000/dynmat4: omega( 3) = 4.077984 [THz] = 136.026917 [cm-1]
> 9000/dynmat5: omega( 1) = -20.410496 [THz] = -680.820848 [cm-1]
> 9000/dynmat5: omega( 2) = -20.306865 [THz] = -677.364092 [cm-1]
> 9000/dynmat5: omega( 3) = -20.306865 [THz] = -677.364092 [cm-1]
> 9000/dynmat6: omega( 1) = -18.152324 [THz] = -605.496350 [cm-1]
> 9000/dynmat6: omega( 2) = -13.489915 [THz] = -449.975145 [cm-1]
> 9000/dynmat6: omega( 3) = 7.302901 [THz] = 243.598557 [cm-1]
> 9000/dynmat7: omega( 1) = -19.840424 [THz] = -661.805304 [cm-1]
> 9000/dynmat7: omega( 2) = -19.840424 [THz] = -661.805304 [cm-1]
> 9000/dynmat7: omega( 3) = -19.840424 [THz] = -661.805304 [cm-1]
> 9000/dynmat8: omega( 1) = 10.185938 [THz] = 339.766315 [cm-1]
> 9000/dynmat8: omega( 2) = 10.185938 [THz] = 339.766315 [cm-1]
> 9000/dynmat8: omega( 3) = 10.185938 [THz] = 339.766315 [cm-1]
> 9500/dynmat1: omega( 1) = -0.590362 [THz] = -19.692343 [cm-1]
> 9500/dynmat1: omega( 2) = -0.590362 [THz] = -19.692343 [cm-1]
> 9500/dynmat1: omega( 3) = -0.590362 [THz] = -19.692343 [cm-1]
> 9500/dynmat2: omega( 1) = -18.238237 [THz] = -608.362092 [cm-1]
> 9500/dynmat2: omega( 2) = -14.917871 [THz] = -497.606611 [cm-1]
> 9500/dynmat2: omega( 3) = -5.360685 [THz] = -178.813195 [cm-1]
> 9500/dynmat3: omega( 1) = 5.116022 [THz] = 170.652121 [cm-1]
> 9500/dynmat3: omega( 2) = 6.910191 [THz] = 230.499164 [cm-1]
> 9500/dynmat3: omega( 3) = 9.840788 [THz] = 328.253358 [cm-1]
> 9500/dynmat4: omega( 1) = -17.878327 [THz] = -596.356802 [cm-1]
> 9500/dynmat4: omega( 2) = -14.055044 [THz] = -468.825819 [cm-1]
> 9500/dynmat4: omega( 3) = 4.075301 [THz] = 135.937407 [cm-1]
> 9500/dynmat5: omega( 1) = -20.413130 [THz] = -680.908710 [cm-1]
> 9500/dynmat5: omega( 2) = -20.309403 [THz] = -677.448775 [cm-1]
> 9500/dynmat5: omega( 3) = -20.309403 [THz] = -677.448775 [cm-1]
> 9500/dynmat6: omega( 1) = -18.153469 [THz] = -605.534553 [cm-1]
> 9500/dynmat6: omega( 2) = -13.491302 [THz] = -450.021402 [cm-1]
> 9500/dynmat6: omega( 3) = 7.301280 [THz] = 243.544500 [cm-1]
> 9500/dynmat7: omega( 1) = -19.842973 [THz] = -661.890323 [cm-1]
> 9500/dynmat7: omega( 2) = -19.842973 [THz] = -661.890323 [cm-1]
> 9500/dynmat7: omega( 3) = -19.842973 [THz] = -661.890323 [cm-1]
> 9500/dynmat8: omega( 1) = 10.185085 [THz] = 339.737862 [cm-1]
> 9500/dynmat8: omega( 2) = 10.185085 [THz] = 339.737862 [cm-1]
> 9500/dynmat8: omega( 3) = 10.185085 [THz] = 339.737862 [cm-1]
> 10000/dynmat1: freq ( 1) = -0.590365 [THz] = -19.692448 [cm-1]
> 10000/dynmat1: freq ( 2) = -0.590365 [THz] = -19.692448 [cm-1]
> 10000/dynmat1: freq ( 3) = -0.590365 [THz] = -19.692448 [cm-1]
> 10000/dynmat2: freq ( 1) = -18.238245 [THz] = -608.362357
> [cm-1]
> 10000/dynmat2: freq ( 2) = -14.917869 [THz] = -497.606564
> [cm-1]
> 10000/dynmat2: freq ( 3) = -5.360684 [THz] = -178.813180
> [cm-1]
> 10000/dynmat3: freq ( 1) = 5.116023 [THz] = 170.652156 [cm-1]
> 10000/dynmat3: freq ( 2) = 6.910189 [THz] = 230.499110 [cm-1]
> 10000/dynmat3: freq ( 3) = 9.840795 [THz] = 328.253573 [cm-1]
> 10000/dynmat4: freq ( 1) = -17.878328 [THz] = -596.356839
> [cm-1]
> 10000/dynmat4: freq ( 2) = -14.055079 [THz] = -468.826956
> [cm-1]
> 10000/dynmat4: freq ( 3) = 4.075245 [THz] = 135.935550 [cm-1]
> 10000/dynmat5: freq ( 1) = -20.413139 [THz] = -680.909014
> [cm-1]
> 10000/dynmat5: freq ( 2) = -20.309404 [THz] = -677.448789
> [cm-1]
> 10000/dynmat5: freq ( 3) = -20.309404 [THz] = -677.448789
> [cm-1]
> 10000/dynmat6: freq ( 1) = -18.153472 [THz] = -605.534658
> [cm-1]
> 10000/dynmat6: freq ( 2) = -13.491303 [THz] = -450.021432
> [cm-1]
> 10000/dynmat6: freq ( 3) = 7.301284 [THz] = 243.544606 [cm-1]
> 10000/dynmat7: freq ( 1) = -19.842972 [THz] = -661.890313
> [cm-1]
> 10000/dynmat7: freq ( 2) = -19.842972 [THz] = -661.890313
> [cm-1]
> 10000/dynmat7: freq ( 3) = -19.842972 [THz] = -661.890313
> [cm-1]
> 10000/dynmat8: freq ( 1) = 10.185084 [THz] = 339.737838 [cm-1]
> 10000/dynmat8: freq ( 2) = 10.185084 [THz] = 339.737838 [cm-1]
> 10000/dynmat8: freq ( 3) = 10.185084 [THz] = 339.737838 [cm-1]
> 10500/dynmat1: freq ( 1) = -0.590364 [THz] = -19.692432 [cm-1]
> 10500/dynmat1: freq ( 2) = -0.590364 [THz] = -19.692432 [cm-1]
> 10500/dynmat1: freq ( 3) = -0.590364 [THz] = -19.692432 [cm-1]
> 10500/dynmat2: freq ( 1) = -18.238223 [THz] = -608.361647
> [cm-1]
> 10500/dynmat2: freq ( 2) = -14.917870 [THz] = -497.606597
> [cm-1]
> 10500/dynmat2: freq ( 3) = -5.360684 [THz] = -178.813170
> [cm-1]
> 10500/dynmat3: freq ( 1) = 5.116022 [THz] = 170.652112 [cm-1]
> 10500/dynmat3: freq ( 2) = 6.910191 [THz] = 230.499148 [cm-1]
> 10500/dynmat3: freq ( 3) = 9.840786 [THz] = 328.253285 [cm-1]
> 10500/dynmat4: freq ( 1) = -17.878328 [THz] = -596.356829
> [cm-1]
> 10500/dynmat4: freq ( 2) = -14.055010 [THz] = -468.824685
> [cm-1]
> 10500/dynmat4: freq ( 3) = 4.075346 [THz] = 135.938912 [cm-1]
> 10500/dynmat5: freq ( 1) = -20.413145 [THz] = -680.909226
> [cm-1]
> 10500/dynmat5: freq ( 2) = -20.309403 [THz] = -677.448780
> [cm-1]
> 10500/dynmat5: freq ( 3) = -20.309403 [THz] = -677.448780
> [cm-1]
> 10500/dynmat6: freq ( 1) = -18.153472 [THz] = -605.534649
> [cm-1]
> 10500/dynmat6: freq ( 2) = -13.491302 [THz] = -450.021408
> [cm-1]
> 10500/dynmat6: freq ( 3) = 7.301281 [THz] = 243.544530 [cm-1]
> 10500/dynmat7: freq ( 1) = -19.842973 [THz] = -661.890327
> [cm-1]
> 10500/dynmat7: freq ( 2) = -19.842973 [THz] = -661.890327
> [cm-1]
> 10500/dynmat7: freq ( 3) = -19.842973 [THz] = -661.890327
> [cm-1]
> 10500/dynmat8: freq ( 1) = 10.185084 [THz] = 339.737839 [cm-1]
> 10500/dynmat8: freq ( 2) = 10.185084 [THz] = 339.737839 [cm-1]
> 10500/dynmat8: freq ( 3) = 10.185084 [THz] = 339.737839 [cm-1]
> 11000/dynmat1: freq ( 1) = -0.590368 [THz] = -19.692544 [cm-1]
> 11000/dynmat1: freq ( 2) = -0.590368 [THz] = -19.692544 [cm-1]
> 11000/dynmat1: freq ( 3) = -0.590368 [THz] = -19.692544 [cm-1]
> 11000/dynmat2: freq ( 1) = -18.238164 [THz] = -608.359663
> [cm-1]
> 11000/dynmat2: freq ( 2) = -14.917869 [THz] = -497.606558
> [cm-1]
> 11000/dynmat2: freq ( 3) = -5.360686 [THz] = -178.813223
> [cm-1]
> 11000/dynmat3: freq ( 1) = 5.116021 [THz] = 170.652098 [cm-1]
> 11000/dynmat3: freq ( 2) = 6.910193 [THz] = 230.499225 [cm-1]
> 11000/dynmat3: freq ( 3) = 9.840788 [THz] = 328.253370 [cm-1]
> 11000/dynmat4: freq ( 1) = -17.878328 [THz] = -596.356825
> [cm-1]
> 11000/dynmat4: freq ( 2) = -14.055063 [THz] = -468.826451
> [cm-1]
> 11000/dynmat4: freq ( 3) = 4.075210 [THz] = 135.934363 [cm-1]
> 11000/dynmat5: freq ( 1) = -20.413252 [THz] = -680.912796
> [cm-1]
> 11000/dynmat5: freq ( 2) = -20.309404 [THz] = -677.448789
> [cm-1]
> 11000/dynmat5: freq ( 3) = -20.309404 [THz] = -677.448789
> [cm-1]
> 11000/dynmat6: freq ( 1) = -18.153474 [THz] = -605.534704
> [cm-1]
> 11000/dynmat6: freq ( 2) = -13.491302 [THz] = -450.021399
> [cm-1]
> 11000/dynmat6: freq ( 3) = 7.301282 [THz] = 243.544563 [cm-1]
> 11000/dynmat7: freq ( 1) = -19.842972 [THz] = -661.890317
> [cm-1]
> 11000/dynmat7: freq ( 2) = -19.842972 [THz] = -661.890317
> [cm-1]
> 11000/dynmat7: freq ( 3) = -19.842972 [THz] = -661.890317
> [cm-1]
> 11000/dynmat8: freq ( 1) = 10.185085 [THz] = 339.737859 [cm-1]
> 11000/dynmat8: freq ( 2) = 10.185085 [THz] = 339.737859 [cm-1]
> 11000/dynmat8: freq ( 3) = 10.185085 [THz] = 339.737859 [cm-1]
>
>
> $ cat pw.in
>
> &CONTROL
> calculation = 'scf'
> outdir = './out/'
> prefix = 'aiida'
> pseudo_dir = './pseudo/'
> restart_mode = 'from_scratch'
> verbosity = 'high'
> /
> &SYSTEM
> degauss = 1.0000000000d-02
> ecutrho = 3.2000000000d+02
> ecutwfc = 4.0000000000d+01
> ibrav = 0
> nat = 1
> nspin = 2
> ntyp = 1
> occupations = 'smearing'
> smearing = 'marzari-vanderbilt'
> starting_magnetization = 3.6000000000d-01
> /
> &ELECTRONS
> conv_thr = 1.0000000000d-10
> mixing_beta = 2.0000000000d-01
> /
> ATOMIC_SPECIES
> Fe 55.845 Fe.pbe-spn-rrkjus_psl.0.2.1-tested-pslib030.UPF
> ATOMIC_POSITIONS angstrom
> Fe 0.0000000000 0.0000000000 0.0000000000
> K_POINTS automatic
> 6 6 6 0 0 0
> CELL_PARAMETERS angstrom
> 1.4167999999 1.4167999999 1.4167999999
> -1.4167999999 1.4167999999 1.4167999999
> -1.4167999999 -1.4167999999 1.4167999999
>
>
> $ cat ph.in
>
> AiiDA calculation
> &INPUTPH
> fildyn = 'dynmat'
> iverbosity = 1
> ldisp = .true.
> nq1 = 4
> nq2 = 4
> nq3 = 4
> outdir = './out/'
> prefix = 'aiida'
> tr2_ph = 1.0000000000d-16
> /
>
>
> --
> Giovanni Pizzi
> Post-doctoral Research Scientist
> EPFL STI IMX THEOS
> MXC 340 (Bâtiment MXC)
> Station 12
> CH-1015 Lausanne (Switzerland)
> Phone: +41 21 69 31124
>
>
>
>
>
>
> _______________________________________________
> Q-e-developers mailing list
> Q-e-developers at qe-forge.org
> http://qe-forge.org/mailman/listinfo/q-e-developers
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