[Pw_forum] negative charge density!

[Mousumi Upadhyay Kahaly]

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
>> /
>>
> ==========================================================================
>>
>>
>>
>>
>> _______________________________________________
>> Pw_forum mailing list
>> Pw_forum at pwscf.org
>> http://www.democritos.it/mailman/listinfo/pw_forum
>>
>
>
>
>
> __________________________________
> Yahoo! Mail
> Stay connected, organized, and protected. Take the tour:
> http://tour.mail.yahoo.com/mailtour.html
>
> _______________________________________________
> Pw_forum mailing list
> Pw_forum at pwscf.org
> http://www.democritos.it/mailman/listinfo/pw_forum
>