Hi everyone,
I would like to use Quantum ESPRESSO to calculate the Raman intensity in rutile
TiO2. The Raman-active modes I find agree very well with experiment, but ph.x
also predicts a handful of negative-frequency modes which I cannot eliminate. I
have tried increasing ecutwfc and the density of k-points in the SCF
calculation, to no effect. I have attached my input/output files below. The
lattice parameters/atomic coordinates result from a vc-relax calculation with a
7x7x11 k-mesh.
If anyone could suggest a fix for this, I would greatly appreciate it.
Thank you for your time,
Connor Wilson
Condensed Matter and Materials Science
Brock University
St. Catharines , ON, CAN
! pw.x
&CONTROL
calculation='scf',
restart_mode='from_scratch',
prefix = 'TiO2',
etot_conv_thr = 1.0d-6,
forc_conv_thr = 1.0d-6,
pseudo_dir = '/home/cw279/pseudo',
outdir = '/home/cw279/projects/def-crandles/cw279/TiO2/ph',
/
&SYSTEM
ibrav = 0,
celldm(1) = 8.6924328,
!celldm(3) = 0.6433300,
nat = 6,
ntyp = 2,
ecutwfc = 200,
ecutrho = 800,
occupations = 'fixed',
/
&ELECTRONS
mixing_beta = 0.7,
conv_thr = 1.0d-10,
/
ATOMIC_SPECIES
Ti 47.867 Ti.pz-hgh.UPF
O 15.9994 O.pz-hgh.UPF
K_POINTS {automatic}
4 4 6 1 1 1
CELL_PARAMETERS {alat}
0.982600556 0.000000000 0.000000000
0.000000000 0.982600556 0.000000000
0.000000000 0.000000000 0.629408068
ATOMIC_POSITIONS {crystal}
Ti 0.5000000000 0.5000000000 0.0000000000
Ti 0.0000000000 0.0000000000 0.5000000000
O 0.6959241507 0.6959241507 0.5000000000
O 0.1959241507 0.8040758493 0.0000000000
O 0.8040758493 0.1959241507 0.0000000000
O 0.3040758493 0.3040758493 0.5000000000
! ph.x
&INPUTPH
tr2_ph = 1.0d-18,
prefix = 'TiO2',
amass(1) = 47.867,
amass(2) = 15.9994,
outdir = '/home/cw279/projects/def-crandles/cw279/TiO2/ph',
epsil = .true.,
trans = .true.,
lraman = .true.,
fildyn = 'TiO2.dyn',
/
0.0 0.0 0.0
! dynmat.in
&INPUT
fildyn = 'TiO2.dyn',
asr = 'simple',
/
! dynmat.out
# mode [cm-1] [THz] IR Raman depol.fact
1 -165.11 -4.9500 132.3930 0.0000 0.3695
2 -113.43 -3.4004 91.9463 0.0000 0.6303
3 -113.43 -3.4004 91.9463 0.0000 0.5188
4 -87.89 -2.6347 0.0000 0.0000 0.2925
5 -0.00 -0.0000 0.0000 0.0000 0.4869
6 -0.00 -0.0000 0.0000 0.0000 0.3389
7 0.00 0.0000 0.0000 0.0000 0.3544
8 122.17 3.6624 0.0000 0.3837 0.7500
9 372.09 11.1551 0.0000 0.0000 0.7144
10 375.77 11.2654 3.9843 0.0000 0.3068
11 375.77 11.2654 3.9843 0.0000 0.4022
12 421.88 12.6475 0.0000 0.0000 0.7072
13 447.56 13.4176 0.0000 239.3889 0.7500
14 447.56 13.4176 0.0000 239.3889 0.7500
15 480.43 14.4028 14.4178 0.0000 0.5190
16 480.43 14.4028 14.4178 0.0000 0.7318
17 601.42 18.0300 0.0000 1203.1157 0.2824
18 815.02 24.4338 0.0000 5.3306 0.7500
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