[Pw_forum] negative charge density!
Eyvaz Isaev
eyvaz_isaev at yahoo.com
Fri Jul 15 00:18:09 CEST 2005
Hi,
At this time I would like just to note that you use
plane waves which means you use periodic boundary
condition, i.e. a supercell.
Bests,
Eyvaz.
--- Mousumi Upadhyay Kahaly <mousumi at jncasr.ac.in>
wrote:
> Respected Sir,
>
> I am trying to do calculations for a
> molecule(Cd-2CH3COO); so
> is there much meaning of taking more k-points
> instead only
> Gamma-pt?
>
> Secondly, I have tested pp.x and the
> chdens.x for Cd crystal
> system(hexagonal) with K_POINTS automatic
> 7 7 6 -6 -6 -5
> and
> ecutwfc = 30.00000 Ry ,
> ecutrho = 240.00000 Ry.
>
> Then also I get a negative charge of
> -0.70243E+00 at the
> output .xsf file & hence in xcrysden plot.
> All these negative charges come
> particularly on the metal
> atom. I have done these testing for Pb crystal
> system also
> with both LDA and GGA pseudopotentials. For LDA
> pseudopotential ( Pb.vdb.UPF) no negative charges
> appear
> whereas for GGA psp( pb_ps.uspp.UPF ) negative
> charges appear.
> So, what is the explanation for this negative
> charges?
>
> Can you please suggest some way out to
> get rid of this
> problem while using GGA pseudopotential?
>
> Best regards,
> mousumi
>
> > Hi,
> >
> > Did you try increase k-points instead of using
> only
> > Gamma-point? Besides, test also a little bit
> larger
> > ecutrho, say 30Ry.
> >
> > Bests,
> > Eyvaz.
> >
> >
> > --- Mousumi Upadhyay Kahaly <mousumi at jncasr.ac.in>
> > wrote:
> >
> >> Hi all,
> >>
> >> This is a resubmission of my mail regarding
> >> charge density calculation.
> >>
> >>
> >
>
--------------------------------------------------------------------------
> >>
> >> Dear all,
> >>
> >> I am trying to do charge analysis for
> >> Cd-di-acetate system. With
> >> the following files for pp.x and then chdens.x,
> as I
> >> am plotting
> >> the isosurfaces of charge densities with
> XCRYSDEN, I
> >> am getting
> >> some negative charge;
> >> Minimum grid value= -0.498760, and maximum
> >> grid value= 1.09220.
> >> How come I get such negative values(mainly around
> >> the Cd atom, as found)
> >> which is not negligible? What is the meaning of
> this
> >> NEGATIVE charge
> >> density? Can anyone please tell me, what is the
> >> mistake that I have made &
> >> what should I do to get rid of this?
> >>
> >> Best
> >> regards, Mousumi.
> >>
> >> 1. Input file for SCF pw.x run:
> >>
> >
>
=========================================================================
> >> &CONTROL
> >> calculation = 'scf' ,
> >> restart_mode = 'from_scratch' ,
> >> tstress =.true.,
> >> outdir =
> >>
> '/export/mousumi/PWSCF_2.0.1/Cd_2CH3COO/ELF/tmp//' ,
> >> pseudo_dir = '/export/mousumi/PWscf_GUI/pseudo/'
> ,
> >> prefix = 'Cd_di_acetate' ,
> >> /
> >> &SYSTEM
> >> ibrav = 8,
> >> celldm(1) = 50.000000,
> >> celldm(2) = 0.30,
> >> celldm(3) = 0.30,
> >> nat = 15,
> >> ntyp = 4,
> >> ecutwfc = 25.00000 ,
> >> ecutrho = 150.00000 ,
> >> nosym = .false. ,
> >> nbnd = 37,
> >> occupations = 'smearing' ,
> >> degauss = 0.003 ,
> >> smearing =
> 'methfessel-paxton' ,
> >> nspin = 1 ,
> >> lda_plus_u = .false. ,
> >> /
> >> &ELECTRONS
> >> conv_thr = 1.0d-12 ,
> >> mixing_beta = 0.3 ,
> >> /
> >> ATOMIC_SPECIES
> >> C 12.01000 C.pbe-van_bm.UPF
> >> H 1.00000 H.pbe-van_bm.UPF
> >> O 15.99990 O.pbe-van_bm.UPF
> >> Cd 112.4000 Cd.pbe-van.UPF
> >> ATOMIC_POSITIONS {angstrom}
> >> O -2.181887203 -0.288129610 -0.491107761
> >> O -1.981730329 -0.473233788 1.733566845
> >> C -2.708815067 -0.432156029 0.673205720
> >> C -4.208743648 -0.532432174 0.801074150
> >> H -4.477821741 -1.131831132 1.680695448
> >> H -4.617325903 0.482417907 0.942246198
> >> H -4.646292897 -0.952999527 -0.113856718
> >> Cd -0.137714936 -0.219807184 0.461048531
> >> C 2.434799121 -0.031519760 0.246012557
> >> O 1.729314564 1.038606335 0.354394821
> >> O 1.885568682 -1.194338232 0.239827517
> >> C 3.936349099 0.076394885 0.148653197
> >> H 4.228550980 1.056061785 -0.250634315
> >> H 4.360345258 -0.025882832 1.161749300
> >> H 4.338742013 -0.738423646 -0.467966988
> >>
> >> K_POINTS {automatic}
> >> 1 1 1 0 0 0
> >>
> >
>
==========================================================================
> >>
> >> 2. After the pw.x run with above file, with files
> in
> >> "tmp" dir, file for pp.x
> >>
> >
>
===========================================================================
> >> &inputpp
> >> prefix = 'Cd_di_acetate'
> >> outdir =
> >>
> '/export/mousumi/PWSCF_2.0.1/Cd_2CH3COO/ELF/tmp//'
> >> filplot = 'Cd_2CH3COO_chden'
> >> plot_num = 0
> >> /
> >>
> >
>
==========================================================================
> >>
> >> 3. Then, input file for chdens.x
> >>
> >
>
==========================================================================
> >> &input
> >> nfile = 1
> >> filepp(1)='Cd_2CH3COO_chden'
> >> iflag = 3
> >> output_format = 5
> >> /
> >>
> >
>
==========================================================================
> >>
> >>
> >>
> >>
> >> _______________________________________________
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> >>
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> >>
> >
> >
> >
> >
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