[Pw_forum] Question About Lowdin Charges

Wed Oct 22 23:11:59 CEST 2014

Funny. Below what I got from crystal GaSb (same cutoff, same 
pseudopotentials, a=6.143 A, atom 1 is Ga, atom 2 is Sb).
It doesn't look so different from what you got.

     Atom #   1: total charge =  13.2233, s =  1.1961, 
     Atom #   1: total charge =  13.2233, p =  2.0327, pz=  0.6776, px=
0.6776, py=  0.6776, 
     Atom #   1: total charge =  13.2233, d =  9.9945, dz2=  1.9994,
dxz=  1.9985, dyz=  1.9985, dx2-y2=  1.9994, dxy=  1.9985, 
     Atom #   2: total charge =  14.7447, s =  1.4391, 
     Atom #   2: total charge =  14.7447, p =  3.3071, pz=  1.1024, px=
1.1024, py=  1.1024, 
     Atom #   2: total charge =  14.7447, d =  9.9986, dz2=  1.9998,
dxz=  1.9997, dyz=  1.9997, dx2-y2=  1.9998, dxy=  1.9997, 

Paolo

On Wed, 2014-10-22 at 11:01 -0400, Vic Bermudez wrote:
> Greetings All,
> 
> I'm doing a two-dimensionally-periodic slab calculation for the GaSb (001)
> surface, and I'm trying to make sense out of the Lowdin charge results from
> projwfc.x.  This is a segment of the relevant output (slightly edited for
> clarity) for atoms in the "bulk" of the slab:
> 
> Sb
>      Atom #  17: total charge =  14.9047, s =  1.6852, p =  3.2209, d =
> 9.9986,
>      Atom #  18: total charge =  14.8065, s =  1.4984, p =  3.3097, d =
> 9.9985,
>      Atom #  19: total charge =  14.7370, s =  1.5752, p =  3.1631, d =
> 9.9988,
>      Atom #  20: total charge =  14.9047, s =  1.6852, p =  3.2209, d =
> 9.9986,
> 
> Ga
>      Atom #  21: total charge =  13.2248, s =  1.1862, p =  2.0448, d =
> 9.9938,
>      Atom #  22: total charge =  13.2300, s =  1.1914, p =  2.0447, d =
> 9.9939,
>      Atom #  23: total charge =  13.2174, s =  1.2033, p =  2.0194, d =
> 9.9947,
>      Atom #  24: total charge =  13.2248, s =  1.1862, p =  2.0448, d =
> 9.9938,
> 
> The free Sb atom has a valence occupancy of d(10), s(2), p(3), and the Ga is
> d(10), s(2), p(1). Since the "total charge" reported by projwfc.x is the
> total electron occupancy, what I think I'm seeing is an Sb charge of about
> 15 - 14.8 = +0.2 and a Ga charge of about 13 - 13.2 = -0.2. This is the
> reverse of what it should be. Sb is the anion, which is why the material is
> called "gallium antimonide" and not "antimony gallide". I've looked at
> previous forum posts on this subject, and I believe that my interpretation
> of the Lowdin numbers is consistent with these discussions.
> 
> Any advice would be much appreciated.
> 
> Thanks,
> Vic Bermudez
> 
> Victor M. Bermudez
> Code 6877
> Naval Research Laboratory
> 4555 Overlook Ave., S.W.
> Washington, DC 20375-5347
> 
> victor.bermudez at nrl.navy.mil
> Phone: 202-767-6728
> FAX: 202-767-1165
> 
> P.S.: In case it helps, here is the input (with a lot of atom positions
> deleted) for the nscf run that generated the input used by the projwfc.x
> run:
> 
> &CONTROL
> calculation='nscf',
> restart_mode='restart',
> title='prepare DOS input for bare surface; #62617',
> pseudo_dir='/lustre/cmf/scratch/b/bermudez/QE_PP/',
> outdir='/lustre/cmf/scratch/b/bermudez/SurfDOS',
> wf_collect=.TRUE.,
> verbosity='default',
> tefield=.TRUE.,
> dipfield=.TRUE.
> /
> 
> &SYSTEM
> ibrav=8,
> a=17.1119841047, b=12.8339880785, c=44.0,
> nat=128,
> ntyp=3,
> ecutwfc=30.0,
> ecutrho=300.0,
> london=.TRUE.,
> nosym=.TRUE.,
> occupations='tetrahedra',
> edir=3,
> eamp=0.0,
> emaxpos=0.5,
> eopreg=0.1,
> input_dft='pw91'
> /
> 
> &ELECTRONS
> electron_maxstep=2000,
> conv_thr=1.0D-9,
> mixing_mode='local-TF'
> /
> 
> ATOMIC_SPECIES
> Ga   69.72   Ga.pw91-n-van.UPF
> Sb  121.75   Sb.pw91-n-van.UPF
> H5    1.25   H.pz-vbc_125.UPF
> 
> ATOMIC_POSITIONS angstrom
> Sb       2.138997330   5.022847724   6.773542341
> Ga       2.138997871  -5.172774747   5.920904901
> Ga       6.303916687   1.112378442   5.961021454
> Sb       6.422475638   3.685129656   6.784913634
> Ga      -6.416994681   1.257691244   6.085010916
> Sb      -6.416994193   3.824801392   6.836466153
> Ga      -2.025921740   1.112378091   5.961021393
> Sb      -2.144480532   3.685129427   6.784912981
> Sb       0.309752603   0.016789605   5.583506326
> Sb       0.021948893   4.297405309   5.001534742
> Sb      -0.337617879  -4.315074540   5.610294615
> .
> .
> .
> H5       5.198446115   0.000002191  -6.285644236    0   0   0
> H5       5.198445769   4.277998300  -6.285643824    0   0   0
> H5       5.198445582  -4.278000175  -6.285643213    0   0   0
> H5      -7.635543283  -0.000001494  -6.285642838    0   0   0
> H5      -7.635543358   4.277997263  -6.285642702    0   0   0
> H5      -7.635543780  -4.277997026  -6.285642281    0   0   0
> H5      -3.357548712  -0.000000728  -6.285641379    0   0   0
> H5      -3.357548071   4.277997544  -6.285641893    0   0   0
> H5      -3.357547485  -4.277997519  -6.285642688    0   0   0
> 
> K_POINTS automatic
> 6 8 1 0 0 0
> 
> 
> 
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-- 
Paolo Giannozzi, Dept. Chemistry&Physics&Environment, 
Univ. Udine, via delle Scienze 208, 33100 Udine, Italy
Phone +39-0432-558216, fax +39-0432-558222 