Thank you all for your response. For computing the Z* and epilson for polar materials, I saw in a couple of tutorials that I have to first compute the dynamic matrix using dynmat.x at the Gamma point setting epsil=.true.. For the remaining q-points, I have to add the non-analytical part in the input of the dynmat.x. Is this the correct for version 6.4.1 or should I just have to set some flags?
Also, is there a difference if I use matdyn.x instead of dynmat.x? Regards, Sheikh On Mon, Dec 30, 2019 at 5:34 PM Stefano de Gironcoli <[email protected]> wrote: > the order of the entries in the pseudopotential list or in the atomic > position list should not affect the result. > > however you are not changing only the order. > > 1) you are also swapping the two atoms... this too should not change > anything but is not the same as changing the order only :) > > 2) the first calculation is metallic (with a quite large gaussian > smearing, 0.05 Ry is ~ 0.7 eV) the second uses the default insulating > setting. THIS may have a big impact, for two reasons: i) the fundamental > gap in AlSb, if I remember correctly, is not very large .. comparable to > the smearing width used; ii) being AlSb a polar material the vibrational > properties have a non analytic component ruled by the macroscopic > dielectric properties (Z*, epsilon_infty) that are disabled in the phonon > calculation of metals (where epsilon_infty diverges). > > Additionally, in the phonon calculation step you should make sure you do > compute Z* and epsilon and include them in the subsequent phonon dispersion > calculation step. > > HTH > > stefano > On 30/12/19 23:07, Sheikh Ziauddin Ahmed wrote: > > I am trying to calculate the phonon dispersion of AlSb. I am getting two > different results depending on how I am introducing the atoms in the SCF > calculation. Will the order of the atom change the symmetry of the zinc > blende AlSb? > > In the first case the input deck is: > &system > ibrav=2, nat=2, ntyp=2, > ecutwfc = 50, ecutrho = 500, > occupations='smearing', > smearing='gauss', > degauss=0.05, > celldm(1)=11.5944146, > / > &electrons > conv_thr = 1.0e-12 > mixing_beta = 0.7 > mixing_mode = 'local-TF' > / > ATOMIC_SPECIES > Al 26.98 al_lda_v1.uspp.F.UPF > Sb 121.76 sb_lda_v1.4.uspp.F.UPF > ATOMIC_POSITIONS (alat) > Al 0.0 0.0 0.0 > Sb 0.25 0.25 0.25 > K_POINTS automatic > 6 6 6 0 0 0 > > In the second case the input deck is: > &system > ibrav=2, nat=2, ntyp=2, > ecutwfc = 50, ecutrho = 500, > !occupations='smearing', > !smearing='gauss', > !degauss=0.05, > celldm(1)=11.5944146, > / > &electrons > conv_thr = 1.0e-12 > mixing_beta = 0.7 > mixing_mode = 'local-TF' > / > ATOMIC_SPECIES > Sb 121.76 sb_lda_v1.4.uspp.F.UPF > Al 26.98 al_lda_v1.uspp.F.UPF > ATOMIC_POSITIONS (alat) > Sb 0.0 0.0 0.0 > Al 0.25 0.25 0.25 > K_POINTS automatic > 6 6 6 0 0 0 > > Thanks in advance! > -- > *Sheikh Ziauddin Ahmed * > PhD Candidate > Charles L. Brown Department of Electrical and Computer Engineering > University of Virginia > Email:sza9wz*@virginia.edu* <[email protected]> > LinkedIn: https://www.linkedin.com/in/sheikh-ziauddin-ahmed > > _______________________________________________ > Quantum ESPRESSO is supported by MaX (www.max-centre.eu/quantum-espresso) > users mailing list > [email protected]https://lists.quantum-espresso.org/mailman/listinfo/users > > _______________________________________________ > Quantum ESPRESSO is supported by MaX (www.max-centre.eu/quantum-espresso) > users mailing list [email protected] > https://lists.quantum-espresso.org/mailman/listinfo/users -- *Sheikh Ziauddin Ahmed * PhD Candidate Charles L. Brown Department of Electrical and Computer Engineering University of Virginia Email:sza9wz*@virginia.edu* <[email protected]> LinkedIn: https://www.linkedin.com/in/sheikh-ziauddin-ahmed
_______________________________________________ Quantum ESPRESSO is supported by MaX (www.max-centre.eu/quantum-espresso) users mailing list [email protected] https://lists.quantum-espresso.org/mailman/listinfo/users
