[QE-users] DOS Calculation for a Molecule of Water
Giuseppe Mattioli
giuseppe.mattioli at ism.cnr.it
Fri Dec 7 10:53:46 CET 2018
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.gil9973 at 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.mattioli at ism.cnr.it>
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