[Pw_forum] problem getting electronuc dipole moment

[Mousumi Upadhyay Kahaly]

Dear All,

          I am trying to compute electronic and ionic dipole moments of an
isolated H2 molecule in a big box. For this, after relaxation, I
am running one scf step followed by a pp.x run and then chdens.x
run(with the option idpol = 1).

          The problem is that, irrespective of the positions of the H2
molecule in the big box, always it comes that charge density
inside the Wigner-Seitz cell = 0.00000000 & hence, electronic
dipole moment is sero. Have I done something wrong may be, while
setting up the input files??? Because this is the case for any
molecule in any position within a box of any size. Can anyone
please help me to get rid of this problem?

          All the inputs files i am using(one case: when the molecule
centre is in the centre of the box) are written below.

                                            Best regards,  mousumi.
==========================================================================
1. Input file for scf run: pw.x input file

 &CONTROL
              calculation = 'scf' ,
                   tstress=.true.,
             restart_mode = 'from_scratch' ,
       outdir =
'/export/mousumi/PWSCF_2.0.1/H2/PostProcess/dipole_mom/tmp2//' ,
                  pseudo_dir = '/export/mousumi/PWscf_GUI/pseudo/' ,
                      prefix = 'H2' ,
 /
 &SYSTEM
                       ibrav = 1,
                   celldm(1) = 30.00000,
                         nat = 2,
                        ntyp = 1,
                     ecutwfc = 30.00000  ,
                     ecutrho = 180.00000 ,
                       nosym = .false. ,
                        nbnd = 5,
                       nspin = 1 ,
                  lda_plus_u = .false. ,
 /
 &ELECTRONS
                    conv_thr = 1.0d-8 ,
    /
 &IONS
                     upscale = 10.0 ,
 /
ATOMIC_SPECIES
    H    1.00000  H.pbe-van_bm.UPF
ATOMIC_POSITIONS {angstrom}
H        7.70055287150   7.70055287150   7.70055287150
H        8.15472682850   8.15472682850   8.15472682850
K_POINTS {automatic}
1  1  1  0  0  0
              mixing_beta = 0.6 ,

=====================================================================
2. With the files created in temp2/ directory from the above run,
                        input file for pp.x
 &inputpp
    prefix  = 'H2'
    outdir =
'/export/mousumi/PWSCF_2.0.1/H2/PostProcess/dipole_mom/tmp2//'
    filplot = 'H2_chdens2'
    plot_num = 0
 /

=======================================================================
3. With the 'H2_chdens2' file created in the above run, file for
                                 running chdens.x
&input
    nfile = 1
    filepp(1)='H2_chdens2'
    iflag = 3
    plot_out = 1
    idpol = 1
    output_format = 5
/

=========================================================================