[Pw_forum] phonon instability
On Aug 24, 2011, at 8:21 PM, GAO Zhe wrote: > As I know, frozen phonon method is not implemented in QE. ??? *ANY* code able to perform total-energy and atomic-force calculations can be used to do frozen phonons ... SB --- Stefano Baroni - SISSA & DEMOCRITOS National Simulation Center - Trieste http://stefano.baroni.me [+39] 040 3787 406 (tel) -528 (fax) / stefanobaroni (skype) La morale est une logique de l'action comme la logique est une morale de la pens?e - Jean Piaget -- next part -- An HTML attachment was scrubbed... URL: http://www.democritos.it/pipermail/pw_forum/attachments/20110824/1b5b8398/attachment-0001.htm
[Pw_forum] phonon instability
no i have calculated correctly because the convergence is good with higher k points second is that i have tested zns,wc,NiAs phase none of them have less enthalpy at 130 gpa other thing is that it is stable at above 250 gpa On Wed, Aug 24, 2011 at 7:38 PM, Mike Mehl wrote: > If the B1 structure is unstable with respect to the B2 structure above > 130 GPa, but the B2 structure is dynamically unstable at and above 130 > GPa, there are two possible conclusions: > > 1) The phonons for the B2 structure were not calculated accurately, or > > 2) There is a competing structure that is lower in enthalpy than B1 or > B2 at 130 GPa > > Without more information, no one can judge which conclusion is correct, > suggest remedies for 1), or possible structure for 2). > > > On 08/23/2011 02:40 PM, bhabya sahoo wrote: > > sir > > i am calculating the phase transition of some carbides > > the transition from B1 to B2 transition occures at 130 gpa by enthalpy > > compparison > > but i am able to find phonon instability at 130 gpa for B1 structure > > but at the same time i am not able to find the dyanamic stability of B2 > > phase > > but it occures high pressure (more than130 gpa ) > > is there any explanation for this ? > > > > is there any relation of thermodyanamical unstability > > and dyanamical unstability simultaneously? > > > > > > answers are highly appriceted with some reson > > > > > > > > > > > > > > > > > > Bd sahoo > > reserch scholar > > barc mumbai > > > > > > > > ___ > > Pw_forum mailing list > > Pw_forum at pwscf.org > > http://www.democritos.it/mailman/listinfo/pw_forum > > > -- > Michael J. Mehl > Head, Center for Computational Materials Science > Naval Research Laboratory Code 6390 > Washington DC > > ___ > Pw_forum mailing list > Pw_forum at pwscf.org > http://www.democritos.it/mailman/listinfo/pw_forum > -- next part -- An HTML attachment was scrubbed... URL: http://www.democritos.it/pipermail/pw_forum/attachments/20110824/9903e9cd/attachment.htm
[Pw_forum] convergence w.r.t ecutwfc
Dear experts, Will you please take a look at my input file and convergence table below: I am using PBE USPP for both hydrogen and boron, but calculating energies using PBEsol. (ecutrho is set to 12* ecutwfc.) My question is: 1. Does it look normal? I was expect to seeing 1mRy accuracy at lower ecutwfc values. 2. I didn't use "occupations" or "smearing" and I didn't get any error in output files. Do they affect the convergence? 3. I want to do vc-relax calculation at high pressure. Based on my table, what ecutwfc do you suggest? Thanks in advance. ecutwfc energy 30 -38.28149597 35 -38.28437812 40 -38.28554856 45 -38.28658930 50 -38.28772083 55 -38.28883141 60 -38.28989311 65 -38.29086868 70 -38.29167889 75 -38.29227767 80 -38.29267847 85 -38.29291696 90 -38.29302834 95 -38.29305836 100 -38.29305908 105 -38.29307545 110 -38.29313486 115 -38.29324982 pseudo_dir = ** outdir = ** prefix = '$a' tstress = .true tprnfor = .true verbosity = 'low' / ibrav = 12 celldm(1) = 8.31479435 celldm(2) = 1.3 celldm(3) = 1.4772727273 celldm(4) = -0.260504508642648 nat= 16 ntyp = 2 ecutwfc = $a ecutrho = `expr 12 \* $a` input_dft= 'pbesol' / / ATOMIC_SPECIES B 10.811B.pbe-n-van_ak.UPF H 1.00794 H.pbe-van_ak.UPF ATOMIC_POSITIONS crystal B0.002 0.146 0.042 H -0.194 0.166 0.140 H0.196 0.294 -0.005 H0.104 -0.019 0.112 B -0.002 -0.146 -0.042 H0.194 -0.166 -0.140 H -0.196 -0.294 0.005 H -0.104 0.019 -0.112 B0.498 0.354 0.542 H0.694 0.334 0.640 H0.304 0.206 0.495 H0.396 0.519 0.612 B0.502 0.646 0.458 H0.306 0.666 0.360 H0.696 0.794 0.505 H0.604 0.481 0.388 K_POINTS automatic 8 8 8 0 0 0 -- Amin Torabi Ph.D. Student Chemistry Department The University *of* Western Ontario London, On Canada, N6A 5B7 Phone: 519-661-2111 Ext: 87871 -- next part -- An HTML attachment was scrubbed... URL: http://www.democritos.it/pipermail/pw_forum/attachments/20110824/72c76d1c/attachment.htm
[Pw_forum] phonon instability
If the B1 structure is unstable with respect to the B2 structure above 130 GPa, but the B2 structure is dynamically unstable at and above 130 GPa, there are two possible conclusions: 1) The phonons for the B2 structure were not calculated accurately, or 2) There is a competing structure that is lower in enthalpy than B1 or B2 at 130 GPa Without more information, no one can judge which conclusion is correct, suggest remedies for 1), or possible structure for 2). On 08/23/2011 02:40 PM, bhabya sahoo wrote: > sir > i am calculating the phase transition of some carbides > the transition from B1 to B2 transition occures at 130 gpa by enthalpy > compparison > but i am able to find phonon instability at 130 gpa for B1 structure > but at the same time i am not able to find the dyanamic stability of B2 > phase > but it occures high pressure (more than130 gpa ) > is there any explanation for this ? > > is there any relation of thermodyanamical unstability > and dyanamical unstability simultaneously? > > > answers are highly appriceted with some reson > > > > > > > > > Bd sahoo > reserch scholar > barc mumbai > > > > ___ > Pw_forum mailing list > Pw_forum at pwscf.org > http://www.democritos.it/mailman/listinfo/pw_forum -- Michael J. Mehl Head, Center for Computational Materials Science Naval Research Laboratory Code 6390 Washington DC
[Pw_forum] vdW functional in Quantum-Espresso
There are large changes in vdW functional part between version 4.3 and 4.3.1 or later. First, the vdW functional is put in GGA correlation part in funct.f90 in 4.3, but in an independent part (non-local part) in funct.f90 in 4.3.1. Second, the ld1.x refuse to generate pseudo-potential for functional containing vdW part like vdW-DF in 4.3.1 for it is non-local but it is possible to generate something in 4.3. So I have some question about vdW functional. 1. In 4.3, does vdW-DF, or "sla+pw+rpb+vdw" as 1/4/4/9 imply the original GGA correlation in revPBE, "pbc" here, is used? As 4.3.1 allow user to specify GGA correlation and vdW correction simultaneously, and vdW-DF in that version is 1/4/4/0/1, is it reasonable to add GGA correlation in the functional and perform further calculation? I note in literature it is said GGA correlation is small so it is neglected. 2. What is the difference of vdW functional correction in vdW-DF1 and vdW-DF2? 3. If it is impossible to get a pseudo-potential of vdW-DF , what functional in pseudo-potential should I specify to perform calculation later? What is the pp generated by 4.3 actually and can they be used in further calculation? Thanks. -- next part -- An HTML attachment was scrubbed... URL: http://www.democritos.it/pipermail/pw_forum/attachments/20110824/e6c3ec4b/attachment.htm
[Pw_forum] Does SOC conflict with HSE06?
Dear all,
Does SOC (spin-orbit coupling) conflict with HSE06 in pwscf?
SOC is ok! HSE06 is also OK! But when combining SOC and HSE06, the calculation
stop at EXX calculation!
This is my input file:
verbosity='default' ! 'high'|'low'|'minimal'
restart_mode='from_scratch' ! 'from_scratch'|'restart'
prefix='PbTe'
pseudo_dir='./'
outdir='./tmp'
calculation = 'scf'
/
ibrav=0
nat=2
ntyp= 2
ecutwfc = 35.0, ecutrho = 140.0 ! ecutrho (4-12*ecutwfc)!
occupations='fixed' ! 'tetrahedra'|'smearing'|'fixed'|
nbnd= 16 ! number of bands, need special
!+ DFT Hybride functional +
input_dft='hse', nqx1 = 1, nqx2 = 1, nqx3 = 1
exxdiv_treatment='g-b' ! yukawa,erfc_simple,vcut_ws,vcut_spheric,none
x_gamma_extrapolation = .true. ! if cut_ws or vcut_spheric, = .false.
!exx_fraction =0.25, screening_parameter=0.16 !see Modules/func.f90
lspinorb=.true.
noncolin=.true.
/
diagonalization='david' ! 'cg'|'-ndiag N'
electron_maxstep=300
conv_thr = 1.0e-8
mixing_mode='plain' ! 'TF'|'local-TF'
mixing_beta = 0.5
mixing_ndim=8
adaptive_thr=.true. ! use for EXX
conv_thr_init=1.d-3 ! use for EXX
conv_thr_multi=1.d-1 ! use for EXX
/
ATOMIC_SPECIES
Pb 207.200 Pb.rel-pbe-nc.UPF
Te 127.600 Te.rel-pbe-nc.UPF
ATOMIC_POSITIONS {crystal}
Pb0.0 0.0 0.0
Te0.5 0.5 0.0
K_POINTS {automatic} !gamma,crystal_b
4 4 4 0 0 0
CELL_PARAMETERS {cubic}
6.104762563 6.104762563 0.0
6.104762563 -6.104762563 0.0
6.104762563 0.0 6.104762563
Best regards,
Longhua Li
2011-08-23
foursea at 163.com
[Pw_forum] phonon instability
sir i am calculating the phase transition of some carbides the transition from B1 to B2 transition occures at 130 gpa by enthalpy compparison but i am able to find phonon instability at 130 gpa for B1 structure but at the same time i am not able to find the dyanamic stability of B2 phase but it occures high pressure (more than130 gpa ) is there any explanation for this ? is there any relation of thermodyanamical unstability and dyanamical unstability simultaneously? answers are highly appriceted with some reson Bd sahoo reserch scholar barc mumbai -- next part -- An HTML attachment was scrubbed... URL: http://www.democritos.it/pipermail/pw_forum/attachments/20110824/4b334281/attachment.htm
[Pw_forum] bulk modulus
i want this by quasi harmonic approximation On Tue, Aug 23, 2011 at 12:07 PM, Stefano Baroni wrote: > using the quasi-harmonic approximation, or constant-pressure ab-initio > molecular dynamics (*) - SB > > (*) if you want a more articulated answer, may I expect a more articulated > and well-thought question? > > On Aug 23, 2011, at 1:46 PM, bhabya sahoo wrote: > > > how can one calculate bulk modulus and elastic constants with tempertaure > by quantum espresso code > > > > > > > > b d sahoo reserch scholar > > barc mumbai > ___ > Pw_forum mailing list > Pw_forum at pwscf.org > http://www.democritos.it/mailman/listinfo/pw_forum > > > --- > Stefano Baroni - SISSA & DEMOCRITOS National Simulation Center - Trieste > http://stefano.baroni.me [+39] 040 3787 406 (tel) -528 (fax) / > stefanobaroni (skype) > > La morale est une logique de l'action comme la logique est une morale de la > pens?e - Jean Piaget > > > ___ > Pw_forum mailing list > Pw_forum at pwscf.org > http://www.democritos.it/mailman/listinfo/pw_forum > > -- next part -- An HTML attachment was scrubbed... URL: http://www.democritos.it/pipermail/pw_forum/attachments/20110823/cde59c24/attachment-0001.htm
