Oh, certo: scusa, dimenticavo. S. -- Stefano Baroni, Trieste -- swift message written and sent on the go
> Il giorno 7 lug 2021, alle ore 10:42, Thomas Brumme > <[email protected]> ha scritto: > > Dear all, > > I think I don't see the wood for the trees and hope that someone can help. > > I want to calculate the phonons for a 2D material using the 2D cutoff > technique. The scf calculations for the well-relaxed system work without a > problem and I also get no error calculating the phonons on a 5x5x1 q-point > grid. The relevant portions of the scf and phonon input are attached below. > All frequencies are positive at every single q point, except the 3 acoustic > branches at the Gamma point which are "only" -10 cm^-1 and -15 cm^-1. > However, the interpolation, in order to get the dispersion, results in one > branch which is negative for quite some portion near Gamma - for the first > half along G-K I have up to -130 cm^-1 and along G-M up to -60 cm^-1. I guess > that this is the out-of-plane acoustic branch and now I wonder if this is > real (i.e., the system is really unstable) or if I make some obvious mistake. > I will also check by explicitly calculating few q points in the relevant > region but before I wanted to ask here. > > Any help would be appreciated! > > Regards > > Thomas Brumme > > -------------------------------------------- > scf: > > &control > calculation = 'scf' > prefix = 'pasc12', > pseudo_dir = '/home/tbrumme/pseudos/pslibrary.1.0.0/rel-pbe/', > outdir = '/scratch/ws/0/tbrumme-pasc/', > verbosity = 'high', > wf_collect = .true., > / > > &system > ibrav = 0, > nat = 14, > ntyp = 3, > ecutwfc = 70.0, > ecutrho = 560, > noncolin = .true., > lspinorb = .true., > vdw_corr = 'DFT-D', > nbnd = 96, > assume_isolated = '2D', > / > > &electrons > conv_thr = 1.D-14, > / > > ATOMIC_SPECIES > C 12.0 'C.rel-pbe-n-kjpaw_psl.1.0.0.UPF' > P 30.973761 'P.rel-pbe-n-kjpaw_psl.1.0.0.UPF' > As 74.921595 'As.rel-pbe-dn-kjpaw_psl.1.0.0.UPF' > > ATOMIC_POSITIONS crystal > ... > > CELL_PARAMETERS angstrom > 6.69668 0.0 0.0 > -3.348340 5.799495 0.0 > 0.0 0.0 15.0 > > K_POINTS automatic > 25 25 1 0 0 0 > > -------------------------------------------- > phonons: > > Phonon dispersions for pasc12 > &inputph > tr2_ph=1.0d-18, > prefix='pasc12', > ldisp=.true., > nq1=5, nq2=5, nq3=1, > outdir='/scratch/ws/0/tbrumme-pasc/', > fildyn='pasc12.dyn.xml', > max_seconds = 83700, > verbosity='high', > recover=.true. > alpha_mix(1)=0.4, > / > > -------------------------------------------- > q2r and matdyn: > > &input > fildyn='pasc12.dyn.xml', flfrc='pasc12.551.fc', loto_2d=.false., > zasr='simple', > / > > &input > flfrc='pasc12.551.fc.xml', flfrq='pasc12.freq', q_in_band_form=.true., > loto_2d=.false., asr='simple', > fldyn='pasc12.dyn.xml' > / > 4 > 0.00000000 0.00000000 0.0 60 > 0.33333333 0.57735027 0.0 30 > 0.00000000 0.57735027 0.0 45 > 0.00000000 0.00000000 0.0 1 > > -- > Dr. rer. nat. Thomas Brumme > Theoretical chemistry > TU Dresden - BAR / II49 > Helmholtzstr. 18 > 01069 Dresden > > Tel: +49 (0)351 463 40844 > > email: [email protected] > > _______________________________________________ > Quantum ESPRESSO is supported by MaX (www.max-centre.eu) > users mailing list [email protected] > https://lists.quantum-espresso.org/mailman/listinfo/users _______________________________________________ Quantum ESPRESSO is supported by MaX (www.max-centre.eu) users mailing list [email protected] https://lists.quantum-espresso.org/mailman/listinfo/users
