[Pw_forum] XANES SiO2
Matteo Calandra
matteo.calandra at impmc.jussieu.fr
Fri Jul 8 09:47:01 CEST 2011
>
> After closer inspection, the major problem was due to unit conversion
> (lattice constants were in Angstroms instead of Bohr). But regarding the
> occupied states: as I understand it, for insulators, one should do an scf
> calculation (without smearing) followed by an xspectra fermi level
> calculation to find the energy to cut the occupied states. In the case of a
> gamma only
> kpoint grid, could one simply use the energy of the highest occupied band
> instead of doing the fermi level calculation?
>
> Thanks,
>
> Max
>
Dear Max,
it is in general a good idea to print out forces/stress, if you had
Angstrom instead of Bohr you probably would have totally absurd values
for Forces and Stress.
Regarding the question about Fermi level in insulators. In general you
can choose your Fermi level as you prefer inside the gap of the system
WITH a core-hole.
All the best, M.
>
> ------------------------------
>
> Message: 4
> Date: Fri, 08 Jul 2011 00:38:20 +0200
> From: Guntram Schmidt<guntram.schmidt at chemie.uni-halle.de>
> Subject: [Pw_forum] dE0s is positive which should never happen
> To: pw_forum at pwscf.org
> Message-ID:<4E16355C.4050708 at chemie.uni-halle.de>
> Content-Type: text/plain; charset=ISO-8859-15; format=flowed
>
> Dear All,
>
> I tried to optimize a crystal structure of a molecular compound and get
> this strange error. Is there something I've forgotten in the input file?
> I've chosen a small ecutwfc to make some "preoptimization" - is it okay
> to do so (I'm still not able to converge the cutoffs - see my other post)?
>
> &control
> calculation = 'relax'
> restart_mode='from_scratch',
> prefix='i2t0480',
> tstress = .true.
> tprnfor = .true.
> pseudo_dir = '/gpfs/home/aasfu/espresso-4.3.1/pseudo/',
> outdir='/gpfs/home/aasfu/tmp/'
> verbosity = 'high'
> /
> &system
> ibrav = 14,
> A = 8.2555,
> B = 17.0986,
> C = 16.3082,
> cosAB = 0,
> cosAC = -.4968073528,
> cosBC = 0,
> nat = 196,
> ntyp = 5,
> occupations = 'fixed',
> ecutwfc = 20,
> ecutrho = 80,
> input_dft = 'vdW-DF'
> /
> &electrons
> conv_thr = 1.0d-5
> electron_maxstep= 1000
> /
> &ions
> /
>
> ATOMIC_SPECIES
> P 39.974 P.rpb-nc.UPF
> O 15.999 O.rpb-nc.UPF
> N 14.007 N.rpb-nc.UPF
> C 12.011 C.rpb-nc.UPF
> H 1.0079 H.rpb-nc.UPF
>
>
> ATOMIC_POSITIONS angstrom
> H -4.163902 3.036540 7.286078 1 1 1
> C -3.730208 5.027159 7.959787 1 1 1
> H -2.669409 4.951703 7.725352 1 1 1
> C -4.231111 6.183196 8.511764 1 1 1
> H -3.568842 7.024960 8.708593 1 1 1
> and 210 more atoms...
>
>
>
> The output says after 41 cycles of geometry optimizations in the
> subroutine stress:
>
>
>
> 0: number of scf cycles = 30
> 0: number of bfgs steps = 28
> 0:
> 0: energy old = -1592.2501932245 Ry
> 0: energy new = -1547.5620256423 Ry
> 0:
> 0: CASE: energy _new> energy _old
> 0:
> 0:
> 0:
> %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
> 0: from bfgs : error # 1
> 0: dE0s is positive which should never happen
> 0:
> %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
> 0:
> 0: stopping ...
>
> The strange thing is, that the energy was not -1592... before at all:
> grep '!' i2t0480.xyz.relax.20.rpb-nc.UPF.out
> 0:! total energy = -1542.41391161 Ry
> 0:! total energy = -1544.87249615 Ry
> 0:! total energy = -1546.30689086 Ry
> 0:! total energy = -1546.89859418 Ry
> 0:! total energy = -1547.07908001 Ry
> 0:! total energy = -1547.12438175 Ry
> 0:! total energy = -1547.16304879 Ry
> 0:! total energy = -1547.21850898 Ry
> 0:! total energy = -1547.26799568 Ry
> 0:! total energy = -1547.31147437 Ry
> 0:! total energy = -1547.33202922 Ry
> 0:! total energy = -1547.35963149 Ry
> 0:! total energy = -1547.36650754 Ry
> 0:! total energy = -1547.38045447 Ry
> 0:! total energy = -1547.38597654 Ry
> 0:! total energy = -1547.39351928 Ry
> 0:! total energy = -1547.40184806 Ry
> 0:! total energy = -1547.41383843 Ry
> 0:! total energy = -1547.43030750 Ry
> 0:! total energy = -1547.45110560 Ry
> 0:! total energy = -1547.47294386 Ry
> 0:! total energy = -1547.48424959 Ry
> 0:! total energy = -1547.48774725 Ry
> 0:! total energy = -1547.49458349 Ry
> 0:! total energy = -1547.50098365 Ry
> 0:! total energy = -1547.50487139 Ry
> 0:! total energy = -1547.50802242 Ry
> 0:! total energy = -1547.51133404 Ry
> 0:! total energy = -1547.51564694 Ry
> 0:! total energy = -1547.52054790 Ry
> 0:! total energy = -1547.52614229 Ry
> 0:! total energy = -1547.53597920 Ry
> 0:! total energy = -1547.54614655 Ry
> 0:! total energy = -1547.55021920 Ry
> 0:! total energy = -1547.55191818 Ry
> 0:! total energy = -1547.55360256 Ry
> 0:! total energy = -1547.55527582 Ry
> 0:! total energy = -1547.55697509 Ry
> 0:! total energy = -1547.55871207 Ry
> 0:! total energy = -1547.56042619 Ry
> 0:! total energy = -1547.56202564 Ry
>
>
> Thanks a lot for help,
> Guntram
>
>
> ------------------------------
>
> Message: 5
> Date: Fri, 08 Jul 2011 11:28:26 +0800
> From: gbliu<goodluck_1982 at 163.com>
> Subject: Re: [Pw_forum] What's wrong in my calculation of epsilon of
> fcc Au?
> To: PWSCF Forum<pw_forum at pwscf.org>, Tao Sun<taotao.sun at gmail.com>
> Message-ID:<4E16795A.9060409 at 163.com>
> Content-Type: text/plain; charset="iso-8859-1"
>
> Dear Sun,
>
> Thanks for your reply. I know this. Automatic k-mesh is only used
> in the scf run. In the following *nscf *run I used a self defined
> k-mesh, which can be seen in the attached file fccAu.nscf4eps.in of the
> original mail.
>
> Best regards,
> Liu Gui-Bin
>
> ? 2011/7/7 23:53, Tao Sun ??:
>> Hi.
>>
>> I have never done dielectric function calculations. But the kmesh you
>> are using "15 15 15 1 1 1" automatic seems to be inconsistent with
>> this manual. https://ir.library.dc-uoit.ca/bitstream/10155/159/3/McNelles_Phillip_appendixA.pdf.
>> Maybe this is worth checking, i.e. set the full kmesh by hand,
>> without symmetry.
>>
>> Best
>>
>> Tao
>>
>> On Thu, Jul 7, 2011 at 4:39 AM, gbliu<goodluck_1982 at 163.com> wrote:
>>> Dear all,
>>>
>>> I want to calculate dielectric function of carbon nanotube, but I have
>>> no experiences of calculating dielectric function before. Hence, I decide to
>>> start with a simple case of fcc gold, because there are referable results
>>> from wien2k (wien2k is capable of simple case such as fcc Au, but too
>>> resource consumptive to deal with large cells such as CNT).
>>> Because epsilon.x doesn't support USPP, the UPF file of Au is got by
>>> converting fhi file from abinit using fhi2upf.x. I calculate fcc Au with
>>> a=7.71bohr and 15x15x15 k-mesh using both pwscf(v4.3) and wien2k. First I
>>> check the band structures and find that the results from both softwares
>>> agree well (see attachments). But the results of epsilon from pwscf is not
>>> satisfactory as the results from wien2k:
>>>
>>> (1) Figures imag_eps and real_eps are the compares with only interband
>>> contribution. (note that for pwscf, I subtract the intraband contribution
>>> [-omega_p^2/omega^2] to get only interband contribution for compares). We
>>> can see the differences are notable. What's the reason?/* */_*BTW, I use a
>>> homogeneous k-mesh also 15x15x15 generated by myself for epsilon calculation
>>> (see input file fccAu.nscf4eps.in).*_
>>> ------input for epsilon.x--------
>>> &inputpp
>>> outdir='./work'
>>> prefix='fccAu'
>>> calculation='eps'
>>> /
>>> &energy_grid
>>> smeartype='gauss'
>>> intersmear=0.1d0
>>> intrasmear=0d0
>>> wmax=20d0
>>> wmin=0d0
>>> nw=600
>>> shift=0d0
>>> /
>>> --------------------------------
>>>
>>> (2) As for the intraband contribution, wien2k gives the plasma frequency
>>> 9.0075eV which agrees well with experimental value (ref:
>>> http://wave-scattering.com/drudefit.html), but the result from epsilon.x is
>>> puzzling.
>>> Specifically, plasma frequency given in the output of epsilon.x is dependent
>>> on the input parameters:
>>> <1>. intrasmear=0, wmax=20d0 --> The bulk xx plasmon frequency [eV] is:
>>> 14.877926200
>>> <2>. intrasmear=0, wmax=10d0 --> The bulk xx plasmon frequency [eV] is:
>>> 7.625822195
>>> <3>. intrasmear=0, wmax=6d0 --> The bulk xx plasmon frequency [eV] is:
>>> 3.156554381
>>> <4>. intrasmear=0.1, wmax=20d0 --> The bulk xx plasmon frequency [eV] is:
>>> 15.766403193
>>> <5>. intrasmear=0.1, wmax=10d0 --> The bulk xx plasmon frequency [eV] is:
>>> 9.322251787
>>> <6>. intrasmear=0.1, wmax=20d0 --> The bulk xx plasmon frequency [eV] is:
>>> 6.263713572
>>> However, none of these values is the one got by fitting the results using
>>> Drude model [ 1 - omega_p^2/(omega^2+i*omega*gamma), gamma is the intrasmear
>>> here ]. By fitting the results using Drude model, I get omega_p=5.528769eV,
>>> for all the cases above (<1>~<6>). But this omega_p is far from the
>>> experimental value (~9 eV)! What's wrong? And what are the meanings of the
>>> values given in<1>~<6> ?
>>>
>>> How can I get more accurate results like the ones from wien2k?
>>> Please help me if you know something about this, thanks in advance!
>>>
>>> Best regards!
>>>
>>> Liu Guibin
>>> Postdoctoral Fellow,
>>> Department of Physics,
>>> The University of Hong Kong
>>> gbliu at hku.hk
>>>
>>>
>>>
>>>
>>>
>>>
>>> _______________________________________________
>>> Pw_forum mailing list
>>> Pw_forum at pwscf.org
>>> http://www.democritos.it/mailman/listinfo/pw_forum
>>>
>>>
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--
* * * *
Matteo Calandra, Directeur de Recherche (DR2)
Institut de Mineralogie et de Physique des Milieux Condenses de Paris
Universite Pierre et Marie Curie, tour 23, 3eme etage, case 115
4 Place Jussieu, 75252 Paris Cedex 05 France
Tel: +33-1-44 27 52 16 Fax: +33-1-44 27 37 85
http://www.impmc.jussieu.fr/~calandra
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