[QE-users] under pressure PbTaSe2 vc-relax calculation
Nicola Marzari
nicola.marzari at epfl.ch
Wed May 26 10:35:44 CEST 2021
Dear all,
1) a perennial recommendation of mine is indeed to make sure the cutoffs
for wfcs and rho are both enough to have the stress well converged -
this was one key critiations for the SSSP (that you can find here
https://www.materialscloud.org/discover/sssp/). Reasonably tuned
parameters and appropriate pseudopotentials for any input structure can
be obtained from here:
https://www.materialscloud.org/work/tools/qeinputgenerator
Your mileage might vary, and you might be able to get away with looser
thresholds, or need tighter ones, but that is a recommended starting
point, to understand what you need.
2) a second recommendaiton in dealing with solids is to use PBEsol
rather than PBE as a first default choice.
As always, test crtically these input parameters to understand how they
are affecting your calculations.
nicola
On 26/05/2021 10:28, Stefano de Gironcoli wrote:
> more than with a different set of k-points, the last scf is done
> resetting the spherical cutoff according to the last cell (during the
> vc-relaxation the G vectors in the list are deformed but the miller
> indices included in the list are not updated and the sphere actually
> deforms into an ellipsoid ).
>
> As the pressure converges slowly with cutoff if the pressure changes
> significantly this is an indication that the cutoff might have been too
> low or that the cell has changed a lot.
>
> stefano
>
> On 26/05/21 09:40, mkondrin wrote:
>> Dear Rencong,
>>
>> I believe that the last step in vc-relax calculations is made in
>> slightly different Brillouin zone (calculated in relaxed variable cell
>> parameters), so the pressure calculated in the last step may be
>> different from whose obtained in the previous step (where Brillouin
>> zone of the original cell was used convergence criteria with desired
>> pressure is checked).
>>
>> It also seems to me that your pressure is rather small. May be it has
>> sense to increase the pressure to at least 10 kbar.
>>
>> Sincerely yours,
>> M. V. Kondrin
>>
>>
>> On 26.05.2021 05:48, 连云龙 wrote:
>>> Dear Rencong,
>>>
>>> I had similar experiences when I use QE pw.x to relax structures
>>> under pressure and I want to follow this conversation.
>>>
>>> My experience is that, the behaviour and result of relaxation depend
>>> largely on the pesudopotential.
>>>
>>> It is also helpful to investigate the energy and pressure during the
>>> relaxation.
>>>
>>> In order for other experts to help you, could you please provide:
>>> (1) the pseudopotentials used in the calculation
>>> (2) the entire output file of pw.x, or at least the section contains
>>> the final coordinates? (search "End of BFGS" in the output file)
>>> (3) your name and affiliation (this is the rule of the mailing list)
>>>
>>> Best,
>>> Yunlong
>>>
>>>
>>>
>>> --
>>> Yunlong LIAN ORCID : https://orcid.org/0000-0002-9474-2181 CSNS,
>>> Dongguan Neutron Science Center Dongguan, Guangdong, P. R. China 连云
>>> 龙 中国散裂中子源 中子科学部 A1-629 (内线 303) 中国广东省东莞市
>>> -----Original Messages-----
>>> From:Amadeus <760158264 at qq.com>
>>> Sent Time:2021-05-25 15:22:02 (Tuesday)
>>> To: users <users at lists.quantum-espresso.org>
>>> Cc:
>>> Subject: [QE-users] under pressure PbTaSe2 vc-relax calculation
>>>
>>>
>>> Dear QE developer
>>>
>>>
>>> I did the structural relaxation calculation for Pb at pressure of
>>> 3kbar， this is relax.in
>>>
>>>
>>> &CONTROL
>>> prefix='PbTaSe2',
>>> calculation='vc-relax', pseudo_dir='../../', outdir='./tmp',
>>> verbosity='high',
>>> tprnfor=.true., tstress=.true., forc_conv_thr=1.0d-4, nstep=100,
>>> /
>>> &SYSTEM
>>> ibrav= 0, nat= 4, ntyp= 3,
>>> occupations = 'smearing', smearing = 'gauss', degauss = 1.0d-2,
>>> ecutwfc = 50, ecutrho = 500,
>>> /
>>> &ELECTRONS
>>> conv_thr = 1.0d-8
>>> mixing_beta = 0.7d0
>>> /
>>> &IONS
>>> /
>>> &CELL
>>> cell_dynamics = "bfgs"
>>> press = 2.70000e+00
>>> press_conv_thr =0.1
>>> /
>>> ATOMIC_SPECIES
>>> Ta 180.9479 Ta.UPF
>>> Pb 207.2 Pb.UPF
>>> Se 78.96 Se.UPF
>>> CELL_PARAMETERS (angstrom)
>>> 3.4834700000 0.0000000000 0.0000000000
>>> -1.7417350000 3.0167735133 0.0000000000
>>> 0.0000000000 0.0000000000 9.4755300000
>>> ATOMIC_POSITIONS (crystal)
>>> Pb 0.0000000000 0.0000000000 0.0000000000
>>> Se 0.0000000000 0.0000000000 0.3246710000
>>> Ta 0.3333330000 0.6666670000 0.5000000000
>>> Se 0.0000000000 0.0000000000 0.6753290000
>>> K_POINTS {automatic}
>>> 15 15 5 0 0 0
>>>
>>>
>>> In relax.in, press=3.0kbar. But after pw.x is done, relax.out show
>>> that total stress (Ry/bohr**3) (kbar) P=-0.83, and This is
>>> inconsistent with press=3. this is part of relax.out
>>>
>>>
>>> [rencong at mu01 phonon]$ grep 'Computing stress (Cartesian axis) and
>>> pressure' -A 15 relax.out
>>>
>>>
>>> ....
>>>
>>>
>>> Computing stress (Cartesian axis) and pressure
>>>
>>>
>>> total stress (Ry/bohr**3) (kbar) P= 2.93
>>> 0.00002030 -0.00000000 0.00000000 2.99 -0.00 0.00
>>> -0.00000000 0.00002030 -0.00000000 -0.00 2.99 -0.00
>>> -0.00000000 0.00000000 0.00001921 -0.00 0.00 2.83
>>>
>>>
>>> kinetic stress (kbar) 26877.23 0.00 0.00
>>> 0.00 26877.23 -0.00
>>> 0.00 0.00 26796.57
>>>
>>>
>>> local stress (kbar)-103340.53 0.03 0.00
>>> 0.03-103340.50 0.00
>>> 0.00 0.00 89394.48
>>>
>>>
>>> nonloc. stress (kbar) 7797.15 0.00 0.00
>>> --
>>> Computing stress (Cartesian axis) and pressure
>>>
>>>
>>> total stress (Ry/bohr**3) (kbar) P= 2.96
>>> 0.00002009 -0.00000000 0.00000000 2.96 -0.00 0.00
>>> -0.00000000 0.00002009 -0.00000000 -0.00 2.96 -0.00
>>> 0.00000000 -0.00000000 0.00002028 0.00 -0.00 2.98
>>>
>>>
>>> kinetic stress (kbar) 26879.49 0.00 0.00
>>> 0.00 26879.49 -0.00
>>> 0.00 -0.00 26798.86
>>>
>>>
>>> local stress (kbar)-103299.75 0.03 0.00
>>> 0.03-103299.72 0.00
>>> 0.00 0.00 89348.84
>>>
>>>
>>> nonloc. stress (kbar) 7797.79 -0.00 0.00
>>> --
>>> Computing stress (Cartesian axis) and pressure
>>>
>>>
>>> total stress (Ry/bohr**3) (kbar) P= -0.83
>>> -0.00000653 -0.00000000 -0.00000000 -0.96 -0.00 -0.00
>>> 0.00000000 -0.00000653 0.00000000 0.00 -0.96 0.00
>>> 0.00000000 0.00000000 -0.00000384 0.00 0.00 -0.56
>>>
>>>
>>> kinetic stress (kbar) 26883.07 0.00 -0.00
>>> 0.00 26883.07 -0.00
>>> -0.00 -0.00 26802.38
>>>
>>>
>>> local stress (kbar)-103303.36 0.03 0.00
>>> 0.03-103303.33 0.00
>>> 0.00 0.00 89345.22
>>>
>>>
>>> nonloc. stress (kbar) 7795.83 -0.00 0.00
>>>
>>>
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>>> users mailing list users at lists.quantum-espresso.org
>>> https://lists.quantum-espresso.org/mailman/listinfo/users
>>
>> _______________________________________________
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> _______________________________________________
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> users mailing list users at lists.quantum-espresso.org
> https://lists.quantum-espresso.org/mailman/listinfo/users
--
----------------------------------------------------------------------
Prof Nicola Marzari, Chair of Theory and Simulation of Materials, EPFL
Director, National Centre for Competence in Research NCCR MARVEL, EPFL
http://theossrv1.epfl.ch/Main/Contact http://nccr-marvel.ch/en/project
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