[Pw_forum] imaginary frequency at extended Q point
潭影空人心
774729155 at qq.com
Tue Oct 20 03:36:53 CEST 2015
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
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