[Pw_forum] Change of occupation number and cut3d
Samuel Poncé
samuel.pon at gmail.com
Sun Jul 31 15:49:43 CEST 2011
Dear Le,
I have normally 8 electrons in my system and define a charge of tot_charge =
+0.00046875. I then have 7.99953125 electrons in my system. I want to do
than so that I can make a finite difference calculation with respect to the
occupation number of my HOMO. As I'm only considering the gamma point of
diamond and as the HOMO is 3X degenerate at that point I decrease the
occupation number of the last 3 valences bands from 2.0 electrons per bands
to 1.99 electrons per bands.
The numbers that occupation numbers gives in the output file of PWSCF is the
occupation number (theoretically 2.0 for the valence band) weighted by the
symmetries of the k point grid.
*Actual behaviour:*
number of k points= 8
cart. coord. in units 2pi/a_0
k( 1) = ( 0.0000000 0.0000000 0.0000000), wk = 0.0312500
k( 2) = ( -0.2500000 0.2500000 -0.2500000), wk = 0.2500000
k( 3) = ( 0.5000000 -0.5000000 0.5000000), wk = 0.1250000
k( 4) = ( 0.0000000 0.5000000 0.0000000), wk = 0.1875000
k( 5) = ( 0.7500000 -0.2500000 0.7500000), wk = 0.7500000
k( 6) = ( 0.5000000 0.0000000 0.5000000), wk = 0.3750000
k( 7) = ( 0.0000000 -1.0000000 0.0000000), wk = 0.0937500
k( 8) = ( -0.5000000 -1.0000000 0.0000000), wk = 0.1875000
And for the gamma point:
k = 0.0000 0.0000 0.0000 ( 1243 PWs) bands (ev):
-7.9264 13.7887 13.7887 13.7887 19.5000 19.5000 19.5000 27.9310
occupation numbers
0.0312 0.0312 0.0312 0.0312 0.0000 0.0000 0.0000 0.0000
*Expected behaviour*
number of k points= 8
cart. coord. in units 2pi/a_0
k( 1) = ( 0.0000000 0.0000000 0.0000000), wk = 0.0312500
k( 2) = ( -0.2500000 0.2500000 -0.2500000), wk = 0.2500000
k( 3) = ( 0.5000000 -0.5000000 0.5000000), wk = 0.1250000
k( 4) = ( 0.0000000 0.5000000 0.0000000), wk = 0.1875000
k( 5) = ( 0.7500000 -0.2500000 0.7500000), wk = 0.7500000
k( 6) = ( 0.5000000 0.0000000 0.5000000), wk = 0.3750000
k( 7) = ( 0.0000000 -1.0000000 0.0000000), wk = 0.0937500
k( 8) = ( -0.5000000 -1.0000000 0.0000000), wk = 0.1875000
And for the gamma point:
k = 0.0000 0.0000 0.0000 ( 1243 PWs) bands (ev):
-7.9264 13.7887 13.7887 13.7887 19.5000 19.5000 19.5000 27.9310
occupation numbers
0.0312 *0.03109375* *0.03109375 **0.03109375 *0.0000
0.0000 0.0000 0.0000
( The bold number corresponds to 1.99/64 )
Here is my input file:
&CONTROL
calculation = "scf" ! scf run
restart_mode = "from_scratch" ! "restart" form an interrupted
run
prefix = "Diamond" ! Basename for all binary files
verbosity = "high" ! Output more informations
wf_collect = .true. ! Collect wf in one single file
pseudo_dir = '$PSEUDO_DIR/'
outdir = '$TMP_DIR/'
tstress = .true. ! If true, print stress
tprnfor = .true. ! If true, print forces
/
&SYSTEM
nbnd = 8 ! 4 valence and 4 cond.
ibrav = 2 ! Correspond to fcc lattice
celldm(1) = 6.66491891 ! Lattice spacing in Bohr
nat = 2 ! Number of atoms
ntyp = 1 ! Number of different atomic type
ecutwfc = 100 ! Wf cutoff in Ry
ecutrho = 400 ! Density cutoff (4*ecutwfc for
nc psp and 9-10 for ultrasoft)
tot_charge = +0.00046875 ! 4-(63*4+3.97)/64
occupations = "fixed"
/
&ELECTRONS
diagonalization = "david" ! Diagonalization method: "david"
or "cg"
conv_thr = 1e-16 ! Energy accuracy threshold in Ry
mixing_beta = 0.5 ! Charge mixing, reduce it if SCF
is unstable
/
ATOMIC_SPECIES
C 12.011 C.pz-vbc.UPF ! Label | mass |
pseudopotential
ATOMIC_POSITIONS {bohr}
C 0.00 0.00 00.00
C 1.66622973 1.66622973 1.66622973
K_POINTS automatic
4 4 4 0 0 0
Best regards,
Samuel Poncé
2011/7/30 Duy Le <ttduyle at gmail.com>
> 2011/7/30 Samuel Poncé <samuel.pon at gmail.com>:
> > I did try to add the variable tot_charge = +0.00046875 because I have 64
> k
> > points and 4 valences band ( 4-(63*4+3.97)/64)
>
> Not sure what you were calculating. tot_charge is additional charge
> you add to your system.
> For example, if you have a system with 8 electron, and if you define
> tot_charge = +1, you will have 8-1=7 electron in the system.
>
> > However if I add the variable 'occupations = "fixed"' then I get the
> > following WARNING:
> > WARNING: integrated charge= 8.00000000, expected= 7.99953125
> >
> > I off course get the exact same total energy as with tot_charge = 0 (this
> is
> > not the expected behaviour).
> >
> > I did try without the variable 'occupation' (by the way what is the
> default
> > value for occupation?) and also get the exact same total energy.
>
> This does not depend on occupation. Read manual about occupation for
> more details.
> If you do a simple math: 7.99953125+0.00046875 you will see a "magic"
> number.
>
>
> > I also do not understand why I don't have an occupation of 2.0 for all my
> > valence states?
> >
> > k = 0.0000 0.0000 0.0000 ( 1243 PWs) bands (ev):
> >
> > -7.9264 13.7887 13.7887 13.7887
> >
> > occupation numbers
> > 0.0312 0.0312 0.0312 0.0312
> you should post your input for further advice.
> --------------------------------------------------
> Duy Le
> PhD Candidate
> Department of Physics
> University of Central Florida.
>
> "Men don't need hand to do things"
>
>
> >
> >
> > 2011/7/30 GAO Zhe <flux_ray12 at 163.com>
> >>
> >> Dear Ponce:
> >> I am sorry that I may not catch the right meaning of your first
> question.
> >> If you mean how to make extra or less charge for a model, you can use
> >> "total_charge" in &system namelist.
> >> If you wanna get information of wavefunction, you'd better read
> >> Doc/INPUT_PP. For the charge density at specified k-point and band, you
> can
> >> calculate |psi|^2 through pp.x. Moreover, if you want to obtain the
> charge
> >> density for all k-points on specified bands, you can summary them by
> pp.x,
> >> too. P.S.: the original code of pp.x can just allow 7 filepp, but you
> can
> >> change the variable, nfilemax, in PP/chdens.f90, then make pp.x.
> >> Good Luck.
> >> --
> >> GAO Zhe
> >> CMC Lab, MSE, SNU, Seoul, S.Korea
> >>
> >> At 2011-07-29 17:27:27,"Samuel Poncé" <samuel.pon at gmail.com> wrote:
> >>
> >> Dear Quantum espresso user/developers,
> >>
> >> I have two questions:
> >>
> >> 1) Is it possible in pwscf to change "by hand" the occupation number (
> and
> >> impose a charge compensation accordingly) and if so how to do it?
> >> I would like to do so because the sum over the different mode of the
> >> partial derivative of the phonon frequency with respect of the
> occupation
> >> number gives the zero point motion renormalization using Brooks theorem.
> I
> >> would like to do this by finite difference (hence doing by hand some
> >> calculation at different occupation number).
> >>
> >> 2) Is it possible to extract informations in text format form the
> >> wavefunctions? What is the right post processing tool to do so? Like
> having
> >> the value of the wavefunction for a defined k points and band index?
> >>
> >> Thanks you!
> >>
> >> Samuel Poncé.
> >> (phD student, Université Catholique de Louvain, Belgium).
> >>
> >>
> >>
> >> _______________________________________________
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> >>
> >
> >
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