[Pw_forum] Backward compatibility issue on elph matrix elements between QE 4.0.3 and 5.1.2
Samuel Poncé
samuel.pon at gmail.com
Sun Jun 28 21:06:56 CEST 2015
Dear Paolo,
Thank you for your reply.
The elphmat internal variable should not be a werewolf as it represent <u_k
| dV_scf/dR | u_k+q >**2, a variable that directly enters physicals
quantities like the zero-point renormalization.
Following your advice I could narrowed it down so far between revision 5000
and 5300 (see below).
Best,
Samuel
QE 4.0.3 q = ( 0.000000000 0.333333333 0.000000000
elphmat(:,:,:)**2 0.1192375
elphmat(:,:,:)**2 0.9861288
elphmat(:,:,:)**2 1.354492
elphmat(:,:,:)**2 0.3075966
espresso-r5000 q = ( 0.000000000 0.333333333 0.000000000
elphmat(:,:,:)**2 0.1192375
elphmat(:,:,:)**2 0.9861288
elphmat(:,:,:)**2 1.354492
elphmat(:,:,:)**2 0.3075966
espresso-r5300 q = ( 0.000000000 0.333333333 0.000000000
elphmat(:,:,:)**2 0.1192376
elphmat(:,:,:)**2 0.9861288
elphmat(:,:,:)**2 1.348592
elphmat(:,:,:)**2 0.3134981
espresso-r5667 q = ( 0.000000000 0.333333333 0.000000000
elphmat(:,:,:)**2 0.1192375
elphmat(:,:,:)**2 0.9861288
elphmat(:,:,:)**2 1.348592
elphmat(:,:,:)**2 0.3134981
espresso-r7654 q = ( 0.000000000 0.333333333 0.000000000
elphmat(:,:,:)**2 0.1192375
elphmat(:,:,:)**2 0.9861287
elphmat(:,:,:)**2 1.348593
elphmat(:,:,:)**2 0.3134982
QE 5.1.2 q = ( 0.000000000 0.333333333 0.000000000 )
elphmat(:,:,:)**2 0.1192376
elphmat(:,:,:)**2 0.9861287
elphmat(:,:,:)**2 1.348592
elphmat(:,:,:)**2 0.3134981
2015-06-27 16:30 GMT+01:00 Paolo Giannozzi <p.giannozzi at gmail.com>:
> You should first of all verify whether the quantity you print depends upon
> the specific choice of irreps/degeneracies/phases of wavefunctions/phases
> of the moon. If you are really sure that the quantity you print should not
> vary across versions, a safe but slow way to figure out what happened when
> and maybe why is to start from a svn version close to 4.0.3 and go up until
> something happens.
>
> Paolo
>
> On Fri, Jun 26, 2015 at 8:23 PM, Samuel Poncé <samuel.pon at gmail.com>
> wrote:
>
>> Dear developers of QE,
>>
>> I noticed a backward compatibility issue on the electron-phonon matrix
>> element between QE 4.0.3 and 5.1.2.
>>
>> I was wondering if it was a bug and if not, what was the reason.
>>
>> I added the following line in the two versions of the code in
>> PHonon/PH/elphon.f90
>>
>> if (ik==215) then
>>
>> write(*,*)'elphmat(:,:,:)**2',SUM((REAL(REAL(elphmat(:,:,:))))**2)+SUM((REAL(AIMAG(elphmat(:,:,:))))**2)
>>
>> This should be a physically relevant quantity that should not change
>> between version (the order of the mode changed but it is not an issue).
>>
>> Test:
>> 6x6x6 q-grid same pseudo, tol and inputs parameters
>>
>> There is 16 irr q-points:
>>
>> ( 16q-points):
>> N xq(1) xq(2) xq(3)
>> 1 0.000000000 0.000000000 0.000000000
>> 2 -0.166666667 0.166666667 -0.166666667
>> 3 -0.333333333 0.333333333 -0.333333333
>> 4 0.500000000 -0.500000000 0.500000000
>> 5 0.000000000 0.333333333 0.000000000
>> 6 -0.166666667 0.500000000 -0.166666667
>> 7 0.666666667 -0.333333333 0.666666667
>> 8 0.500000000 -0.166666667 0.500000000
>> 9 0.333333333 0.000000000 0.333333333
>> 10 0.000000000 0.666666667 0.000000000
>> 11 0.833333333 -0.166666667 0.833333333
>> 12 0.666666667 -0.000000000 0.666666667
>> 13 0.000000000 -1.000000000 0.000000000
>> 14 0.666666667 -0.333333333 1.000000000
>> 15 0.500000000 -0.166666667 0.833333333
>> 16 -0.333333333 -1.000000000 0.000000000
>>
>> All the elphmat**2 are the same (up to 4 digits) for 13 of the 16
>> q-points. For example
>>
>> QE 5.1.2 q = ( -0.166666667 0.166666667 -0.166666667 )
>> elphmat(:,:,:)**2 0.5446267
>> elphmat(:,:,:)**2 0.5446253
>> elphmat(:,:,:)**2 0.9506719
>> elphmat(:,:,:)**2 0.9506719
>>
>> freq ( 1) = 9.137536 [THz] = 304.795384 [cm-1]
>> freq ( 2) = 9.137536 [THz] = 304.795384 [cm-1]
>> freq ( 3) = 15.052865 [THz] = 502.109513 [cm-1]
>> freq ( 4) = 39.653912 [THz] = 1322.712114 [cm-1]
>> freq ( 5) = 39.653912 [THz] = 1322.712114 [cm-1]
>> freq ( 6) = 40.741956 [THz] = 1359.005377 [cm-1]
>>
>> QE 4.0.3 q = ( -0.166666667 0.166666667 -0.166666667 )
>> elphmat(:,:,:)**2 0.5446267
>> elphmat(:,:,:)**2 0.9506719
>> elphmat(:,:,:)**2 0.5446266
>> elphmat(:,:,:)**2 0.9506719
>>
>> omega( 1) = 9.137611 [THz] = 304.799915 [cm-1]
>> omega( 2) = 9.137611 [THz] = 304.799915 [cm-1]
>> omega( 3) = 15.052641 [THz] = 502.105399 [cm-1]
>> omega( 4) = 39.653770 [THz] = 1322.716173 [cm-1]
>> omega( 5) = 39.653770 [THz] = 1322.716173 [cm-1]
>> omega( 6) = 40.741800 [THz] = 1359.009209 [cm-1]
>>
>>
>> But the three irr-q* 5, 10* and *16* are NOT the same:
>> QE 5.1.2 q = ( 0.000000000 0.333333333 0.000000000 )
>> elphmat(:,:,:)**2 0.1192376
>> elphmat(:,:,:)**2 0.9861287
>> elphmat(:,:,:)**2 1.348592
>> elphmat(:,:,:)**2 0.3134981
>>
>> freq ( 1) = 11.633039 [THz] = 388.036416 [cm-1]
>> freq ( 2) = 11.633039 [THz] = 388.036416 [cm-1]
>> freq ( 3) = 16.188917 [THz] = 540.004156 [cm-1]
>> freq ( 4) = 39.110566 [THz] = 1304.588071 [cm-1]
>> freq ( 5) = 39.110566 [THz] = 1304.588071 [cm-1]
>> freq ( 6) = 40.947507 [THz] = 1365.861806 [cm-1]
>>
>> QE 4.0.3 q = ( 0.000000000 0.333333333 0.000000000
>> elphmat(:,:,:)**2 0.3075966
>> elphmat(:,:,:)**2 1.354492
>> elphmat(:,:,:)**2 0.1192375
>> elphmat(:,:,:)**2 0.9861288
>>
>> omega( 1) = 11.633152 [THz] = 388.042751 [cm-1]
>> omega( 2) = 11.633152 [THz] = 388.042751 [cm-1]
>> omega( 3) = 16.188922 [THz] = 540.007888 [cm-1]
>> omega( 4) = 39.110425 [THz] = 1304.592025 [cm-1]
>> omega( 5) = 39.110425 [THz] = 1304.592025 [cm-1]
>> omega( 6) = 40.947359 [THz] = 1365.865939 [cm-1]
>>
>> As you can see the difference for the 0,1/3,0 is not huge but
>> significant. As a matter of fact when
>> I'm using the dvscf produced by QE 4 or 5 for that irr-q it can lead to
>> physically very different results. Therefore I would like to know which
>> dvscf file is correct (QE 4 or 5)?
>>
>> Thank you,
>>
>> Best Regards,
>>
>> Samuel Ponce
>> Department of Materials, University of Oxford
>>
>>
>>
>>
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>> Pw_forum at pwscf.org
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>>
>
>
>
> --
> Paolo Giannozzi, Dept. Chemistry&Physics&Environment,
> Univ. Udine, via delle Scienze 208, 33100 Udine, Italy
> Phone +39-0432-558216, fax +39-0432-558222
>
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