Hi Pietro, Using v5.1 or v6.4, I get the correct answer. Perhaps there was a bug in v6.3MaX, or maybe there is just a problem with my build. In any case, I have a working build of 6.4 now so problem solved.
Thanks! Casey ________________________________ From: users <[email protected]> on behalf of Casey Brock <[email protected]> Sent: Wednesday, March 27, 2019 12:44 PM To: Quantum Espresso users Forum Subject: Re: [QE-users] incorrect LO-TO splitting for CaO and MgO I am using v.6.3MaX Casey ________________________________ From: users <[email protected]> on behalf of Pietro Davide Delugas <[email protected]> Sent: Wednesday, March 27, 2019 11:20 AM To: [email protected] Subject: Re: [QE-users] incorrect LO-TO splitting for CaO and MgO Hi Casey using your inputs cut and paste I get the right values. # mode [cm-1] [THz] IR 1 -0.00 -0.0000 0.0000 2 -0.00 -0.0000 0.0000 3 0.00 0.0000 0.0000 4 291.10 8.7268 11.3884 5 291.10 8.7268 11.3884 6 569.57 17.0753 11.3884 What version are you using ? On 03/27/2019 03:19 PM, Casey Brock wrote: I am using pw.x -> ph.x -> dynmat.x to get the LO and TO phonon frequencies at gamma for rock-salt CaO. The value for the LO phonon I am getting differs from experiment and other DFPT calculations in the literature by 5 THz (167 cm^-1). Perhaps this is a problem with Quantum Espresso, but it’s very possible I’m doing something wrong. I’ve included results and input files below, and any advice would be greatly appreciated. The TO and LO frequencies in THz are given below. Notice that Quantum Espresso using DFPT gives a value that is too low. experiment: 8.9, 17.1 frozen phonon (Phonopy + Quantum Espresso): 8.71, 17.1 DFPT (Quantum Espresso, pw.x->ph.x->dynmat.x): 8.53, 12.2 If I use Phonopy (frozen phonon technique) combined with Quantum Espresso (pw.x and ph.x) I get the correct splitting at gamma. I have tried the same calculation with MgO and I see the same problem, where the frozen phonon technique works while DFPT does not. Here are some things I have tried: different PAW pseudopotentials, increasing ecutwfc and ecutrho, increasing k-points, reducing conv_thr, and reducing tr2_ph. Thanks in advance, Casey Brock input to pw.x ------------------------------------------- &control calculation='scf' restart_mode='from_scratch' prefix='cao' pseudo_dir = './' outdir='./output/' tprnfor = .true. tstress = .true. / &system ibrav = 0 nat = 2 ntyp = 2 ecutwfc = 70.0 ecutrho = 280.0 / &electrons conv_thr = 1.0d-10 mixing_beta = 0.7 / K_POINTS {automatic} 12 12 12 0 0 0 CELL_PARAMETERS bohr 4.45 4.45 0 0 4.45 4.45 4.45 0 4.45 ATOMIC_SPECIES O 16.00 O.pz-n-kjpaw_psl.0.1.UPF Ca 40.08 Ca.pz-spn-kjpaw_psl.1.0.0.UPF ATOMIC_POSITIONS crystal Ca 0.0 0.0 0.0 O 0.5 0.5 0.5 input to ph.x --------------------------------------- Phonon for CaO &inputph prefix='cao', outdir='./output/', fildyn='dyn.G' epsil = .true. tr2_ph=1.0d-14, / 0 0 0 input to dynmat.x --------------------------------------- &input fildyn = 'dyn.G' asr = 'simple' q(1)=0.0, q(2)=0.0, q(3)=1.0 / _______________________________________________ users mailing list [email protected]<mailto:[email protected]> https://lists.quantum-espresso.org/mailman/listinfo/users
_______________________________________________ users mailing list [email protected] https://lists.quantum-espresso.org/mailman/listinfo/users
