[QE-users] under pressure PbTaSe2 vc-relax calculation
Stefano de Gironcoli
degironc at sissa.it
Wed May 26 10:28:31 CEST 2021
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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