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]
https://lists.quantum-espresso.org/mailman/listinfo/users
_______________________________________________
users mailing list
[email protected]
https://lists.quantum-espresso.org/mailman/listinfo/users
