Greeting, QE users!
I meet problems when I want to calculate IR spectrum and free energy of
isolated CO molecule using fqha.x code.
At first I run opt with high precision:
&CONTROL
calculation = 'relax'
forc_conv_thr = 3.8e-5
outdir = './CO/'
prefix = 'scf'
pseudo_dir = './'
restart_mode = 'restart'
tefield = .FALSE.
verbosity = 'high'
wf_collect = .TRUE.
/
&SYSTEM
degauss = 0.002
ecutrho = 300
ecutwfc = 50
ibrav = 0
nat = 2
noncolin = .FALSE.
nspin = 1
ntyp = 2
vdw_corr = 'grimme-d3'
/
&ELECTRONS
conv_thr = 1e-10
electron_maxstep = 100
mixing_beta = 0.1
mixing_mode = 'plain'
scf_must_converge = .TRUE.
startingwfc = 'file'
/
&IONS
ion_dynamics = 'bfgs'
/
ATOMIC_SPECIES
C 12.0107 C.pbe-n-kjpaw_psl.1.0.0.UPF
O 15.9994 O.pbe-n-kjpaw_psl.0.1.UPF
K_POINTS {automatic}
1 1 1 0 0 0
CELL_PARAMETERS {angstrom}
20.00000 0.00000 0.00000
0.00000 20.00000 0.00000
0.00000 0.00000 20.00000
ATOMIC_POSITIONS {angstrom}
C 10.50000000 10.00000000 10.00000000
O 9.50000000 10.00000000 10.00000000
then I run ph.x to get dynamic matrix:
&INPUTPH
outdir='./CO/'
prefix='scf'
tr2_ph=1.0d-12
ldisp=.TRUE.
nq1=1
nq2=1
nq3=1
epsil=.TRUE.
trans=.TRUE.
asr=.TRUE.
/
I want to get IR spectrum by dynmat.x:
&input
fildyn='./matdyn1'
asr='zero-dim'
/
,and q2r.x, matdyn.x to obtain phonon DOS:
input of q2r.x:
&INPUT
fildyn='./matdyn'
zasr='zero-dim'
flfrc='default.fc'
/
input of matdyn.x:
&INPUT
asr='zero-dim'
flfrc='default.fc'
dos=.TRUE.
nk1=1
nk2=1
nk3=1
amass(1) = 12.0107
amass(2) = 15.9994
/
However,
1. I obtained no IR information in ouptut of dynmat.x, The output file ends
with:"
...Force constants read
...epsilon and Z* read
Acoustic Sum Rule: || Z*(ASR) - Z*(orig)|| = 1.057617E+00
Acoustic Sum Rule: ||dyn(ASR) - dyn(orig)||= 8.730790E-01
", and I have no idea about it. :(
2. The DOS value, second column of DOS file (obtained from matdyn.x) is full of
0.000000E+00, although I've got correct vibration frequencies in the output of
ph.x. After consideration, I doubt whether it is meaningful to obtain "regular"
DOS pattern of isolated molecule, cuz according to my understanding, DOS of
isolated molecule is discrete and may contain several delta functions, rather
than a continuum function of frequencies of bulk material. Is this the reason
why I get full-of-zero phonon DOS? If so, should I smooth DOS manually?
There's also a relevant question: I've calculated another system in which CO is
absorbed. Vibration information of CO is obtained as usual, however, DOS value
of frequencies near CO stretching mode frequency are zero, which is similar
with what I get in my isolated CO case. DO these two problems have the same
reason? Or I made the same mistake when I calculate these two systems?
Answers will be appreciated. :)
Best regards!
Yike Huang, PhD candidate.
Dalian Institute of Chemical Physics.
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