[Pw_forum] imaginary frequency at extended Q point

[Sridhar Sadasivam]

Try reducing the tr2_ph parameter. 1D-11 is too high. I have had similar
problems in the past and it was solved by reducing tr2_ph. I would suggest
trying 1D-13 or 1D-14.
-Sridhar
Purdue University

On Mon, Oct 19, 2015 at 9:36 PM, 潭影空人心 <774729155 at qq.com> wrote:

> Dear all,
>    I used nq1 = 2, nq2 = 2, nq3 = 2 and nq1 = 4, nq2 = 4, nq3 = 4
> ,respectively, to do a phonon calculation. There is no imaginary
> frequency at the calculated Q points, but after calculations of Q2R and
> MATDYN, imaginary frequencies appear near GAMMA point(not GAMMA point).
>
> My settings are as follows:
> 1.lattice relaxation under pressure:
> &control
>     calculation               = 'vc-relax'
>
>     restart_mode              = 'from_scratch'
>     prefix                    = 'cras'
>
>     pseudo_dir                = '/data1/tan1/software/espresso-5.1/pseudo/'
>     outdir                    = './tempdir/'
>     etot_conv_thr             = 1.0D-6
>     forc_conv_thr             = 1.0D-4
>     tstress                   = .true.
>     tprnfor                   = .true.
>
> /
> &system
>     ibrav                     = 8
>     A                         = 5.58
>     B                         = 3.36
>     C                         = 6.17
>     nat                       = 8
>     ntyp                      = 4
>     ecutwfc                   = 120
>     occupations               = 'smearing'
>     smearing                  = 'methfessel-paxton'
>     degauss                   = 0.04
>     nspin                     = 2
>     starting_magnetization(1) = -1
>     starting_magnetization(2) = 1
>     starting_magnetization(3) = 0
>     starting_magnetization(4) = 0
> /
> &electrons
>     electron_maxstep          = 100
>     conv_thr                  = 1.0d-6
>     mixing_beta               = 0.7
>
> /
> &ions
>     ion_dynamics             = 'bfgs'
> /
> &cell
>    press                     = 1500
>    cell_dynamics             = 'bfgs'
>    press_conv_thr            = 0.1
>    cell_factor               = 2.5d0
> /
> ATOMIC_SPECIES
>    Cr1   51.9961       Cr.pz-hgh.UPF
>    Cr2   51.9961       Cr.pz-hgh.UPF
>    As1   74.9216       As.pz-hgh.UPF
>    As2   74.9216       As.pz-hgh.UPF
> ATOMIC_POSITIONS (crystal)
> Cr1   0.012000      0.250000      0.201000  1 0 1
> Cr2   0.988000      0.750000      0.799000  1 0 1
> Cr2   0.512000      0.250000      0.299000  1 0 1
> Cr1   0.488000      0.750000      0.701000  1 0 1
> As1   0.195000      0.250000      0.582000  1 0 1
> As2   0.805000      0.750000      0.418000  1 0 1
> As2   0.695000      0.250000      0.918000  1 0 1
> As1   0.305000      0.750000      0.082000  1 0 1
> K_POINTS {automatic}
>
> 6 8 6 0 0 0
>
>
> 2.interior coordination relaxation:
> All is the same as above, but "ecutwfc = 50"
> 3.self-consistent iteration for phonon calculation:
> &control calculation = 'scf' restart_mode = 'from_scratch' prefix = 'cras'
> pseudo_dir = '/data1/tan1/software/espresso-5.1/pseudo/' outdir =
> './tempdir/' tstress = .true. tprnfor = .true. / &system ibrav = 0
> celldm(1) = 10.54467182 nat = 8 ntyp = 4 ecutwfc = 50 occupations =
> 'smearing' smearing = 'methfessel-paxton' degauss = 0.05 nspin = 2
> starting_magnetization(1) = -1 starting_magnetization(2) = 1
> starting_magnetization(3) = 0 starting_magnetization(4) = 0 / &electrons
> electron_maxstep = 200 conv_thr = 1.0d-10 mixing_beta = 0.7 /
> ATOMIC_SPECIES Cr1 51.9961 Cr.pz-hgh.UPF Cr2 51.9961 Cr.pz-hgh.UPF As1
> 74.9216 As.pz-hgh.UPF As2 74.9216 As.pz-hgh.UPF CELL_PARAMETERS (alat=
> 10.54467182) 0.9146 0.0000 0.0000 0.0000 0.4765 0.0000 0.0000 0.0000 0.9628
> ATOMIC_POSITIONS (crystal) Cr1 0.0104 0.2500 0.1827 Cr2 0.9896 0.7500
> 0.8173 Cr2 0.5104 0.2500 0.3173 Cr1 0.4896 0.7500 0.6827 As1 0.1833 0.2500
> 0.5616 As2 0.8167 0.7500 0.4384 As2 0.6833 0.2500 0.9384 As1 0.3167 0.7500
> 0.0616 K_POINTS {automatic} 6 8 6 0 0 0
> 4.self-consistent iteration for electron-phonon coupling:
> All is the same as phonon calculation but k-mesh 12 16 12,and in addition
> to "la2F = .true.".
> 5.phonon calculation:
> &inputph tr2_ph = 1.0d-11 prefix = 'cras' fildvscf = 'crasdv' amass(1) =
> 51.9961 amass(2) = 51.9961 amass(3) = 74.9216 amass(4) = 74.9216 outdir =
> './tempdir/', fildyn = 'cras.dyn', electron_phonon='interpolated'
> el_ph_sigma = 0.005, el_ph_nsigma = 10, trans = .true. ldisp = .true.
> alpha_mix(1) = 0.5 recover =.true. nq1 = 2 nq2 = 2 nq3 = 2 /
> 6.q2r:
> &input zasr='crystal', fildyn='cras.dyn', flfrc='cras222.fc', la2F=.true. /
> 7.&input asr='crystal',
> amass(1)=51.9961,amass(2)=51.9961,amass(3)=74.9216,amass(4)=74.9216,
> flfrc='cras222.fc', flfrq='cras.freq', q_in_band_form=.true.,
> la2F=.true.,dos=.false. / 8 0.000000 0.000000 0.000000 50 0.500000 0.000000
> 0.000000 50 0.500000 0.785906 0.000000 50 0.000000 0.000000 0.000000 50
> 0.000000 0.000000 0.456275 50 0.500000 0.000000 0.456275 50 0.500000
> 0.785906 0.456275 50 0.000000 0.000000 0.456275 1
>
> I am eagerly hoping someone can help me.
>
> Thank you.
>
>
> tanlin
>
> 2015.10.20
>
>
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