> Using a k-points grid that includes the K point can be a source of troubles, > I would recommend using 16x16x1 or even 32x32x1 for better results. p.s. and treat it as a metal, adding some smearing, to avoid the absurd dielectric constant
-- Lorenzo Paulatto - Paris On Mar 30 2021, at 5:00 pm, Lorenzo Paulatto <[email protected]> wrote: > You have specified the q-points in crystal fractionary units, hence you have > to specify q_in_cryst_coord=.true. > This can be safely used in conjunction with q_in_band_form, which is a > completely unrelated option. > > Also: > You way of specifying the cell parameters is discouraged and may cause > problems with symmetry detection, but it should work. > > > > Using a k-points grid that includes the K point can be a source of > > troubles, I would recommend using 16x16x1 or even 32x32x1 for better > > results. > hth > -- > Lorenzo Paulatto - Paris > > On Mar 30 2021, at 4:19 pm, Evgenii <[email protected]> wrote: > > Dear Quantum Espresso experts, > > > > I am having trouble calculating the phonon bands of graphene. > > > > First, I took the cif-file of the already relaxed graphite cell from the > > Materials Project site https://next-gen.materialsproject.org/ and made > > graphene cell from it by hand. > > Then I relaxed the cell obtained with vc-relax and 12x12x1 k-point set. > > I used the same parameters to perform a scf calculation: > > > > &CONTROL > > calculation='scf' > > title='graphene' > > prefix='graphene' > > verbosity='high' > > restart_mode='from_scratch' > > nstep=1000 > > iprint=1 > > tstress=.true. > > tprnfor=.true. > > disk_io='default' > > pseudo_dir = '/home/mxm2/Desktop/Graphene', > > outdir='/home/mxm2/Desktop/Graphene/temp' > > / > > &SYSTEM > > ibrav = 0, > > celldm(1)=1.889726, > > nat = 2, > > ntyp = 1, > > ecutwfc = 60.0 , > > ecutrho = 480.0 , > > / > > &ELECTRONS > > electron_maxstep = 1000, > > conv_thr = 1.0d-12 , > > mixing_mode = 'plain' , > > mixing_beta = 0.7d0 , > > / > > ATOMIC_SPECIES > > C 12.011 C.pz-rrkjus.UPF > > ATOMIC_POSITIONS (crystal) > > C 0.000000000 0.000000000 0.000861580 > > C 0.333333000 0.666667000 0.000838420 > > CELL_PARAMETERS (alat) > > 2.438515837 -0.000000000 0.000000000 > > -1.219257919 2.111816662 0.000000000 > > -0.000000000 -0.000000000 19.995916314 > > > > K_POINTS automatic > > 12 12 1 0 0 0 > > > > Then, I run ph.in calculation: > > > > &inputph > > recover=.true. > > tr2_ph=1.0d-14, > > prefix='graphene', > > ldisp=.true. > > nq1=12, > > nq2=12, > > nq3=1, > > amass(1)=12.011, > > outdir='/home/mxm2/Desktop/Graphene/temp', > > fildyn='graphene.dyn', > > / > > > > My q2r: > > > > &input > > fildyn='graphene.dyn', > > zasr='simple', > > flfrc='graphene.12x12x1.fc' > > / > > > > Matdyn input: > > > > &input > > asr='simple', > > amass(1)=12.011, > > flfrc='graphene.12x12x1.fc', > > flfrq='graphene.disp.freq' > > q_in_band_form=.true., > > / > > 4 ! number of q-points > > 0.000 0.000 0.000 10 ! gamma point > > 0.500 0.000 0.000 10 ! M > > 0.333 0.333 0.000 10 ! K > > 0.000 0.000 0.000 1 ! gamma point > > > > Plotband: > > > > graphene.disp.freq > > 0 1600 > > graphene.disp.freq.dat > > graphene.disp.freq.ps > > 0 > > 100 0 > > > > Why the phonon dispersion does not match the pictures from the papers and > > for calculations with e.g. 18x18x1 k-point and nq-point sets the output > > file of graphene.dyn1 look like: > > > > Dielectric Tensor: > > > > ************************ 166.332153320312 0.000000000000 > > 166.332275390625************************ 0.000000000000 > > 0.000000000000 0.000000000000 1.116060253916 > > > > Effective Charges E-U: Z_{alpha}{s,beta} > > > > atom # 1 > > -11117471.575740195811 -0.002632206306 0.000000000000 > > -0.002632205375-11117471.579664016142 0.000000000000 > > 0.000000000000 0.000000000000 -0.003734609171 > > > > Also, what is the best way to set the lattice parameters, via Ibrav or > > CELL_PARAMETERS? > > > > Any help is appreciated. > > > > Best regards, > > Evgeniy Sysoev. > > > > > > _______________________________________________ > > Quantum ESPRESSO is supported by MaX (www.max-centre.eu) > > users mailing list [email protected] > > https://lists.quantum-espresso.org/mailman/listinfo/users >
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