[Pw_forum] imaginary frequency at extended Q point
Shuai
zhao-shuai at edu.life.kyutech.ac.jp
Tue Oct 20 09:41:10 CEST 2015
Dear Tanlin,
I cannot give you suggestions but I have a confusion that you relaxed
the structure under 120 Ry of ecutwfc but for the SCF calculation you
used 50 Ry.
I guess the total energy for 50 Ry SCF is NOT lowest (to some extent)
with the structure relaxed by 120 Ry. I am not sure whether it will
finally impact the result. Why you reduce the Ecut so significantly?
Best wishes,
Shuai
On 10/20/2015 04:19 PM, Lorenzo Paulatto wrote:
> Dear 潭影空人心,
> the imaginary frequencies could just be an artifact of the Fourier
> interpolation procedure, which means that you need to do the ph.x calculation
> on a finer grid.. If that is not possible, your best bet is to try to push
> convergence a bit and try to change the method of acoustic sum rule used.
>
> hth
>
> On Tuesday, October 20, 2015 09:36:53 AM 潭影空人心 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.
>> tanlin2015.10.20
--
PhD candidate
Graduate School of Life Science and Systems Engineering
Kyushu Institute of Technology, Japan
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