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
