The gap of InAs is not correct with PBE. Your system is probably metallic. Please check the gap before computing the dielectric constant.
HTH, Andrea On Tue, 2015-09-08 at 17:48 +0800, Zhiping Xu wrote: > Dear all: > > I am using pw.x and ph.x to calculate the dielectric constant of InAs, and > here are some problems with the calculations. > > (1) After structural relaxation using vc-relax, the stress is now zero > (confirmed using scf calculations for the final structure). > > convergence has been achieved in 10 iterations > > Forces acting on atoms (Ry/au): > > atom 1 type 1 force = 0.00000000 0.00000000 0.00000000 > atom 2 type 2 force = 0.00000000 0.00000000 0.00000000 > > Total force = 0.000000 Total SCF correction = 0.000000 > > > entering subroutine stress ... > > total stress (Ry/bohr**3) (kbar) P= 0.00 > 0.00000001 -0.00000000 -0.00000000 0.00 -0.00 -0.00 > -0.00000000 0.00000001 0.00000000 -0.00 0.00 0.00 > -0.00000000 0.00000000 0.00000001 -0.00 0.00 0.00 > > > However, the following phonon calculation predicts not only negative phonon > frequency at q = 0, but also very strange dielectric constant. > > Dielectric constant in cartesian axis > > ( -230.720680077 -0.000000000 0.000000000 ) > ( -0.000000000 -230.720680077 0.000000000 ) > ( 0.000000000 0.000000000 -230.720680077 ) > > Effective charges (d Force / dE) in cartesian axis > > atom 1 In > Ex ( 9.55076 0.00000 0.00000 ) > Ey ( 0.00000 9.55076 0.00000 ) > Ez ( 0.00000 0.00000 9.55076 ) > atom 2 As > Ex ( -9.43886 0.00000 0.00000 ) > Ey ( -0.00000 -9.43886 -0.00000 ) > Ez ( 0.00000 0.00000 -9.43886 ) > > Diagonalizing the dynamical matrix > > q = ( 0.000000000 0.000000000 0.000000000 ) > > ************************************************************************** > freq ( 1) = -6.064621 [THz] = -202.293974 [cm-1] > freq ( 2) = -6.064621 [THz] = -202.293974 [cm-1] > freq ( 3) = -6.064621 [THz] = -202.293974 [cm-1] > freq ( 4) = 0.164141 [THz] = 5.475159 [cm-1] > freq ( 5) = 0.164141 [THz] = 5.475159 [cm-1] > freq ( 6) = 0.164141 [THz] = 5.475159 [cm-1] > ************************************************************************** > > The input files are attached below for your reference. > > (2) One more question, the vc-relax calculation converges at zero stress, > which was calculated using the cut-off set for initial cell parameters, so > one has to redo the calculations using the new cell parameters following the > suggestion at http://www.quantum-espresso.org/faq/self-consistency/#6.11 > <http://www.quantum-espresso.org/faq/self-consistency/#6.11>. Is there any > better (more automatic) way to obtain a final relaxed cell/atom structures? > > Could any one help me on these two questions? > > Thank you, > > Zhiping > > input files: > > —scf.in— > &control > calculation = 'scf', > restart_mode = 'from_scratch', > pseudo_dir = '/home/xuzp/bin/lib/upf_files', > outdir = '.', > prefix = 'InAs', > tstress = .true. > tprnfor = .true. > wf_collect = .true. > / > &system > ibrav = 2, > celldm(1) = 11.69675, > nat = 2, > ntyp = 2, > ecutwfc = 90, > / > &electrons > diagonalization = 'cg' > conv_thr = 1.0d-10 > / > > ATOMIC_SPECIES > In 111.818 In.pbe-dn-rrkjus_psl.0.2.2.UPF > As 74.920 As.pbe-n-rrkjus_psl.0.2.UPF > > ATOMIC_POSITIONS crystal > In 0.00 0.00 0.00 > As 0.25 0.25 0.25 > > K_POINTS automatic > 9 9 9 0 0 0 > > —ph.in— > phonons of InAs > &inputph > tr2_ph = 1.0d-16, > niter_ph = 100, > prefix = 'InAs', > epsil = .true. > amass(1) = 111.818, > amass(2) = 74.920, > outdir = '.', > fildyn = 'InAs.matdyn', > / > 0.0 0.0 0.0 > _______________________________________________ Pw_forum mailing list > [email protected] http://pwscf.org/mailman/listinfo/pw_forum -- Andrea Dal Corso Tel. 0039-040-3787428 SISSA, Via Bonomea 265 Fax. 0039-040-3787249 I-34136 Trieste (Italy) e-mail: [email protected] _______________________________________________ Pw_forum mailing list [email protected] http://pwscf.org/mailman/listinfo/pw_forum
