I think that given your Bravais lattice nk3 must be equal to nk1 so 10 nk2 10 0 0 0 or 6 nk2 6 0 0 0 should be fine
10 nk2 6 0 0 0 is not the automatic unfolding of a grid generate additional points but this does not mean they form a regular grid. think about what happens for an hexagonal lattice with a shifted grid. stefano On 08/08/2016 17:51, Thomas Brumme wrote: > Dear all, > > I want to calculate the phonon frequencies on a regular q mesh specified > by using > ldisp=.true. and the nq1, nq2, nq3 variables. Yet, I always get the error > > q-mesh breaks symmetry > > even if the grid has the same dimensions as the k mesh in the PWscf > calculation. > This is weird as the q mesh is exactly the same as the k mesh, which was > created > by applying the symmetries to a regular grid. The system is LCO and the > input for > PWscf (in the reduced cell) is: > > &control > calculation = 'scf', > restart_mode = 'from_scratch', > prefix = 'LCO', > pseudo_dir = './', > outdir = './tmp/', > nstep = 300, > wf_collect = .true., > / > &system > ibrav = 0, > nat = 14, > ntyp = 3, > ecutwfc = 200, > occupations = 'smearing', > smearing = 'gauss', > degauss = 0.01, > nspin = 2, > starting_magnetization(3) = 0.02, > nr1 = 128, > nr2 = 128, > nr3 = 128, > / > &electrons > electron_maxstep = 250, > diagonalization = 'cg', > conv_thr = 1.0d-10, > / > CELL_PARAMETERS (angstrom) > 5.261112503 0.000000000 0.000000000 > 0.000000000 5.330947322 0.000000000 > -2.630556252 -0.000000000 6.548827231 > ATOMIC_SPECIES > La 138.90547 La1.UPF > O 15.999 O.pz-n-mt.UPF > Cu 63.546 Cu1.UPF > K_POINTS automatic > 10 10 6 0 0 0 > ATOMIC_POSITIONS (crystal) > ... > > I defined the FFT grid by hand since then the code does not drop the > symmetries > including fractional translations... Could this be the problem? Or that > I did choose > a FFT grid which has the same number of points in x/y/z directions? Or > could this > be due to a similar problem" as in hexagonal crystals where shifting the > k mesh > away from Gamma is a bad idea? Or is there an obvious error in my input > for ph.x: > > &inputph > tr2_ph = 1.0d-18, > prefix = 'LCO', > amass(1) = 138.90547, > amass(2) = 15.999, > amass(3) = 63.546, > outdir = './tmp/', > fildyn = 'LCO.dynG', > ldisp=.true., > nq1=10, nq2=10, nq3=6, > fildvscf = 'LCO.dvscf', > verbosity = 'high', > / > > I searched the archive however I couldn't find a solution to my problem. > Thus, any > help would be very much appreciated :) > > Regards > > Thomas > _______________________________________________ Pw_forum mailing list [email protected] http://pwscf.org/mailman/listinfo/pw_forum
