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Hi Pietro,</div>
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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.</div>
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Thanks!</div>
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Casey</div>
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<div id="divRplyFwdMsg" dir="ltr"><font face="Calibri, sans-serif" style="font-size:11pt" color="#000000"><b>From:</b> users <users-bounces@lists.quantum-espresso.org> on behalf of Casey Brock <casey.brock@hotmail.com><br>
<b>Sent:</b> Wednesday, March 27, 2019 12:44 PM<br>
<b>To:</b> Quantum Espresso users Forum<br>
<b>Subject:</b> Re: [QE-users] incorrect LO-TO splitting for CaO and MgO</font>
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I am using v.6.3MaX</div>
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Casey</div>
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<div id="x_divRplyFwdMsg" dir="ltr"><font face="Calibri, sans-serif" color="#000000" style="font-size:11pt"><b>From:</b> users <users-bounces@lists.quantum-espresso.org> on behalf of Pietro Davide Delugas <pdelugas@sissa.it><br>
<b>Sent:</b> Wednesday, March 27, 2019 11:20 AM<br>
<b>To:</b> users@lists.quantum-espresso.org<br>
<b>Subject:</b> Re: [QE-users] incorrect LO-TO splitting for CaO and MgO</font>
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<div class="x_x_moz-cite-prefix">Hi Casey <br>
using your inputs cut and paste I get the right values. <br>
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# mode [cm-1] [THz] IR<br>
1 -0.00 -0.0000 0.0000<br>
2 -0.00 -0.0000 0.0000<br>
3 0.00 0.0000 0.0000<br>
4 291.10 8.7268 11.3884<br>
5 291.10 8.7268 11.3884<br>
6 569.57 17.0753 11.3884<br>
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What version are you using ? <br>
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On 03/27/2019 03:19 PM, Casey Brock wrote:<br>
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<span style="font-family:Helvetica; font-size:12px; font-weight:normal; orphans:auto; widows:auto; display:inline!important">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.</span>
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<div>The TO and LO frequencies in THz are given below. Notice that Quantum Espresso using DFPT gives a value that is too low.</div>
<div>experiment: 8.9, 17.1</div>
<div>frozen phonon (Phonopy + Quantum Espresso): 8.71, 17.1</div>
<div>DFPT (Quantum Espresso, pw.x->ph.x->dynmat.x): 8.53, <b>12.2</b></div>
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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.</div>
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Thanks in advance,</div>
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Casey Brock</div>
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input to pw.x</div>
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&control<br>
calculation='scf'<br>
restart_mode='from_scratch'<br>
prefix='cao'<br>
pseudo_dir = './'<br>
outdir='./output/'<br>
tprnfor = .true.<br>
tstress = .true.<br>
/<br>
&system<br>
ibrav = 0<br>
nat = 2<br>
ntyp = 2<br>
ecutwfc = 70.0<br>
ecutrho = 280.0<br>
/<br>
&electrons<br>
conv_thr = 1.0d-10<br>
mixing_beta = 0.7<br>
/<br>
K_POINTS {automatic}<br>
12 12 12 0 0 0<br>
<br>
CELL_PARAMETERS bohr<br>
4.45 4.45 0<br>
0 4.45 4.45<br>
4.45 0 4.45<br>
ATOMIC_SPECIES<br>
O 16.00 O.pz-n-kjpaw_psl.0.1.UPF<br>
Ca 40.08 Ca.pz-spn-kjpaw_psl.1.0.0.UPF<br>
ATOMIC_POSITIONS crystal<br>
Ca 0.0 0.0 0.0<br>
O 0.5 0.5 0.5</div>
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input to ph.x</div>
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---------------------------------------</div>
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Phonon for CaO<br>
&inputph<br>
prefix='cao',<br>
outdir='./output/',<br>
fildyn='dyn.G'<br>
epsil = .true.<br>
tr2_ph=1.0d-14,<br>
/<br>
0 0 0</div>
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input to dynmat.x<br>
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&input<br>
fildyn = 'dyn.G'<br>
asr = 'simple'<br>
q(1)=0.0, q(2)=0.0, q(3)=1.0<br>
/</div>
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