Dear Dan
When you compare experimental results and DFT-based results you must
be very careful and you must know very well the limits of theory
itself and the limits of the specitic exchange-correlation functional
you apply. In your case:
1) you are comparing Kohn-Sham orbitals, a single-particle auxiliary
basis having no strict relationship with physical quantities, with an
intrinsically many-body excitation or ionization process.
2) your PBE functional suffers a strong delocalization error. So even
if you trust in the assignment of binding energies to Kophn-Sham
orbitals (which is not entirely correct), you are strongly
overestimating orbitals energies.
You can recover an acceptable description of small isolated systems
such as molecules by using, for example, the CAM-B3LYP functional,
which is unfortunately not available in plane-wave codes like QE. For
a decent description you should use a PBE0 or B3LYP functional
together with the assume_isolated='mt' option which decouples the
electrostatic interaction of the water dipole with its periodicaly
repeated images.
HTH
Giuseppe
Dan Gil <dan.gil9...@gmail.com> ha scritto:
Hi,
I am trying out a DOS calculation for a molecule of water, however, my
results are very inaccurate compared to literature (
http://www1.lsbu.ac.uk/water/water_methods.html). I was wondering if you
could give me some advice on improving my results. I am expecting states at
-14, -15, -19, and -37 eV. Instead, I am getting states at -7, -9, -13, and
-25 eV.
I am first carrying out an SCF calculation of a water molecule (pw.x) and
then obtaining the density of states (dos.x). The structure of water is
already relaxed.
The relevant files are contained below.
- - - - - -water.pw.in
&control
calculation='scf',
wf_collect = .true. ,
outdir = 'water' ,
restart_mode = 'from_scratch' ,
pseudo_dir = 'pseudo' ,
disk_io = 'low' ,
verbosity = 'low' ,
max_seconds = 68000 ,
/
&system
ibrav = 4,
celldm(1)=19.174,
celldm(3)=1,
nat = 3 ,
ntyp = 2 ,
ecutwfc = 70.0,
ecutrho = 560.0,
smearing='gaussian',
occupations='fixed',
/
&electrons
diagonalization='david',
mixing_mode = 'local-TF',
/
&ions
/
ATOMIC_SPECIES
O 15.999 O.pbe-n-rrkjus_psl.1.0.0.UPF
H 1.00794 H.pbe-rrkjus_psl.1.0.0.UPF
ATOMIC_POSITIONS crystal
H 0.003478196 0.090739324 0.224999603
H 0.090739324 0.003478196 0.224999603
O 0.105782480 0.105782480 0.225000794
K_POINTS gamma
- - - - - -
- - - - - - get.dos.in
&dos
outdir = 'water' ,
DeltaE = .1
/
- - - - - -
- - - - - - pwscf.dos
# E (eV) dos(E) Int dos(E) EFermi = 0.000 eV
-25.473 0.1393E-02 0.1393E-03
-25.373 0.2067E+00 0.2081E-01
-25.273 0.4151E+01 0.4359E+00
-25.173 0.1128E+02 0.1564E+01
-25.073 0.4151E+01 0.1979E+01
-24.973 0.2067E+00 0.2000E+01
-24.873 0.1393E-02 0.2000E+01
-24.773 0.1270E-05 0.2000E+01
-24.673 0.1567E-09 0.2000E+01
-24.573 0.2617E-14 0.2000E+01
-24.473 0.5916E-20 0.2000E+01
-24.373 0.1810E-26 0.2000E+01
-24.273 0.7492E-34 0.2000E+01
-24.173 0.4198E-42 0.2000E+01
-24.073 0.3183E-51 0.2000E+01
-23.973 0.3266E-61 0.2000E+01
-23.873 0.4536E-72 0.2000E+01
-23.773 0.8994E-84 0.2000E+01
-23.673 0.6246E-85 0.2000E+01
-23.573 0.6246E-85 0.2000E+01
-23.473 0.6246E-85 0.2000E+01
-23.373 0.6246E-85 0.2000E+01
-23.273 0.6246E-85 0.2000E+01
-23.173 0.6246E-85 0.2000E+01
-23.073 0.6246E-85 0.2000E+01
-22.973 0.6246E-85 0.2000E+01
-22.873 0.6246E-85 0.2000E+01
-22.773 0.6246E-85 0.2000E+01
-22.673 0.6246E-85 0.2000E+01
-22.573 0.6246E-85 0.2000E+01
-22.473 0.6246E-85 0.2000E+01
-22.373 0.6246E-85 0.2000E+01
-22.273 0.6246E-85 0.2000E+01
-22.173 0.6246E-85 0.2000E+01
-22.073 0.6246E-85 0.2000E+01
-21.973 0.6246E-85 0.2000E+01
-21.873 0.6246E-85 0.2000E+01
-21.773 0.6246E-85 0.2000E+01
-21.673 0.6246E-85 0.2000E+01
-21.573 0.6246E-85 0.2000E+01
-21.473 0.6246E-85 0.2000E+01
-21.373 0.6246E-85 0.2000E+01
-21.273 0.6246E-85 0.2000E+01
-21.173 0.6246E-85 0.2000E+01
-21.073 0.6246E-85 0.2000E+01
-20.973 0.6246E-85 0.2000E+01
-20.873 0.6246E-85 0.2000E+01
-20.773 0.6246E-85 0.2000E+01
-20.673 0.6246E-85 0.2000E+01
-20.573 0.6246E-85 0.2000E+01
-20.473 0.6246E-85 0.2000E+01
-20.373 0.6246E-85 0.2000E+01
-20.273 0.6246E-85 0.2000E+01
-20.173 0.6246E-85 0.2000E+01
-20.073 0.6246E-85 0.2000E+01
-19.973 0.6246E-85 0.2000E+01
-19.873 0.6246E-85 0.2000E+01
-19.773 0.6246E-85 0.2000E+01
-19.673 0.6246E-85 0.2000E+01
-19.573 0.6246E-85 0.2000E+01
-19.473 0.6246E-85 0.2000E+01
-19.373 0.6246E-85 0.2000E+01
-19.273 0.6246E-85 0.2000E+01
-19.173 0.6246E-85 0.2000E+01
-19.073 0.6246E-85 0.2000E+01
-18.973 0.6246E-85 0.2000E+01
-18.873 0.6246E-85 0.2000E+01
-18.773 0.6246E-85 0.2000E+01
-18.673 0.6246E-85 0.2000E+01
-18.573 0.6246E-85 0.2000E+01
-18.473 0.6246E-85 0.2000E+01
-18.373 0.6246E-85 0.2000E+01
-18.273 0.6246E-85 0.2000E+01
-18.173 0.6246E-85 0.2000E+01
-18.073 0.6246E-85 0.2000E+01
-17.973 0.6246E-85 0.2000E+01
-17.873 0.6246E-85 0.2000E+01
-17.773 0.6246E-85 0.2000E+01
-17.673 0.6246E-85 0.2000E+01
-17.573 0.6246E-85 0.2000E+01
-17.473 0.6246E-85 0.2000E+01
-17.373 0.6246E-85 0.2000E+01
-17.273 0.6246E-85 0.2000E+01
-17.173 0.6246E-85 0.2000E+01
-17.073 0.6246E-85 0.2000E+01
-16.973 0.6246E-85 0.2000E+01
-16.873 0.6246E-85 0.2000E+01
-16.773 0.6246E-85 0.2000E+01
-16.673 0.6246E-85 0.2000E+01
-16.573 0.6246E-85 0.2000E+01
-16.473 0.6246E-85 0.2000E+01
-16.373 0.6246E-85 0.2000E+01
-16.273 0.6246E-85 0.2000E+01
-16.173 0.6246E-85 0.2000E+01
-16.073 0.6246E-85 0.2000E+01
-15.973 0.6246E-85 0.2000E+01
-15.873 0.6246E-85 0.2000E+01
-15.773 0.6246E-85 0.2000E+01
-15.673 0.6246E-85 0.2000E+01
-15.573 0.6246E-85 0.2000E+01
-15.473 0.6246E-85 0.2000E+01
-15.373 0.6246E-85 0.2000E+01
-15.273 0.6246E-85 0.2000E+01
-15.173 0.6246E-85 0.2000E+01
-15.073 0.6246E-85 0.2000E+01
-14.973 0.6246E-85 0.2000E+01
-14.873 0.6246E-85 0.2000E+01
-14.773 0.6246E-85 0.2000E+01
-14.673 0.6246E-85 0.2000E+01
-14.573 0.6246E-85 0.2000E+01
-14.473 0.6246E-85 0.2000E+01
-14.373 0.6326E-85 0.2000E+01
-14.273 0.1156E-73 0.2000E+01
-14.173 0.1102E-62 0.2000E+01
-14.073 0.1422E-52 0.2000E+01
-13.973 0.2484E-43 0.2000E+01
-13.873 0.5870E-35 0.2000E+01
-13.773 0.1878E-27 0.2000E+01
-13.673 0.8127E-21 0.2000E+01
-13.573 0.4761E-15 0.2000E+01
-13.473 0.3775E-10 0.2000E+01
-13.373 0.4050E-06 0.2000E+01
-13.273 0.5881E-03 0.2000E+01
-13.173 0.1156E+00 0.2012E+01
-13.073 0.3074E+01 0.2319E+01
-12.973 0.1106E+02 0.3426E+01
-12.873 0.5389E+01 0.3964E+01
-12.773 0.3553E+00 0.4000E+01
-12.673 0.3170E-02 0.4000E+01
-12.573 0.3827E-05 0.4000E+01
-12.473 0.6255E-09 0.4000E+01
-12.373 0.1383E-13 0.4000E+01
-12.273 0.4140E-19 0.4000E+01
-12.173 0.1677E-25 0.4000E+01
-12.073 0.9192E-33 0.4000E+01
-11.973 0.6820E-41 0.4000E+01
-11.873 0.6847E-50 0.4000E+01
-11.773 0.9304E-60 0.4000E+01
-11.673 0.1711E-70 0.4000E+01
-11.573 0.4263E-82 0.4000E+01
-11.473 0.6246E-85 0.4000E+01
-11.373 0.6246E-85 0.4000E+01
-11.273 0.6246E-85 0.4000E+01
-11.173 0.6246E-85 0.4000E+01
-11.073 0.6246E-85 0.4000E+01
-10.973 0.6246E-85 0.4000E+01
-10.873 0.6246E-85 0.4000E+01
-10.773 0.6246E-85 0.4000E+01
-10.673 0.6246E-85 0.4000E+01
-10.573 0.8307E-84 0.4000E+01
-10.473 0.4196E-72 0.4000E+01
-10.373 0.3039E-61 0.4000E+01
-10.273 0.2979E-51 0.4000E+01
-10.173 0.3953E-42 0.4000E+01
-10.073 0.7098E-34 0.4000E+01
-9.973 0.1725E-26 0.4000E+01
-9.873 0.5672E-20 0.4000E+01
-9.773 0.2525E-14 0.4000E+01
-9.673 0.1521E-09 0.4000E+01
-9.573 0.1240E-05 0.4000E+01
-9.473 0.1368E-02 0.4000E+01
-9.373 0.2042E+00 0.4021E+01
-9.273 0.4126E+01 0.4434E+01
-9.173 0.1128E+02 0.5562E+01
-9.073 0.4176E+01 0.5979E+01
-8.973 0.2092E+00 0.6000E+01
-8.873 0.1418E-02 0.6001E+01
-8.773 0.1301E-05 0.6001E+01
-8.673 0.1615E-09 0.6001E+01
-8.573 0.2713E-14 0.6001E+01
-8.473 0.6170E-20 0.6001E+01
-8.373 0.1899E-26 0.6001E+01
-8.273 0.7908E-34 0.6001E+01
-8.173 0.4457E-42 0.6001E+01
-8.073 0.1524E-39 0.6001E+01
-7.973 0.1495E-31 0.6001E+01
-7.873 0.1985E-24 0.6001E+01
-7.773 0.3567E-18 0.6001E+01
-7.673 0.8674E-13 0.6001E+01
-7.573 0.2855E-08 0.6001E+01
-7.473 0.1272E-04 0.6001E+01
-7.373 0.7666E-02 0.6001E+01
-7.273 0.6254E+00 0.6064E+01
-7.173 0.6905E+01 0.6754E+01
-7.073 0.1032E+02 0.7786E+01
-6.973 0.2086E+01 0.7995E+01
-6.873 0.5710E-01 0.8000E+01
- - - - - -
Best Regards,
Dan Gil
PhD Candidate
Department of Chemical and Biomolecular Engineering
Case Western Reserve University
GIUSEPPE MATTIOLI
CNR - ISTITUTO DI STRUTTURA DELLA MATERIA
Via Salaria Km 29,300 - C.P. 10
I-00015 - Monterotondo Scalo (RM)
Mob (*preferred*) +39 373 7305625
Tel + 39 06 90672342 - Fax +39 06 90672316
E-mail: <giuseppe.matti...@ism.cnr.it>
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