[Pw_forum] Lowdin Charge- sign

[David Grifith]

Dear Heather

Thanks for your comments. I think that this type of charge (Lowdin) which is
nearly the number of valence electrons can not speak about the details of
the system.
Some electrons are bonding and also, the effect of the core (core electron +
nucleus ) is not negligible. I want to compare the real charge of two atoms
in my system with each other not their valence electrons. I appreciate your
help in advance.

-- 
Sincerely Yours
David G.
JCU

Dear David,
>
> You are right in that the Lowdin charges here refer to the valence
> electrons
> of your system.
>
> The Lowdin charges are calculated as a sum of the projections of the
> extended plane wave valence states onto a pseudo-atomic basis
> (characterized
> by the highest valence s, p, d, f states per your output).
>
> The numbers are positive and not negative, as you pointed out, because they
> refer to the *number* of electrons (i.e. s, p, and so on).  In your
> example,
> there appears to be approximately four electrons: 1 s-type and 3 p-type
> valence electrons attributed to each atom.
>
> The code should also a 'spilling parameter' at the bottom of your output
> that tells you how well the projections are capturing the description of
> the
> valence states.   For instance, the projection is capturing 3.96 electrons
> per atom in your example.  So, if you expect in your example to have four
> valence electrons per atom, then the pseudo-atomic basis is capturing your
> extended valence states pretty well.
>
> Hope that helps!
> --
> Heather K
> Postdoc at Stanford University
>
> On Fri, Dec 10, 2010 at 5:54 PM, David Grifith <david.grifith at gmail.com
> >wrote:
>
> > Dear QE Users
> >
> > My calculated "Lowdin Charge" values are "positive" as shown below. I
> > thought that they must be the charge of the valence electron ! but the
> sign
> > is positive. Also, I don't know that a pseudopotential package like
> Quantum
> > Espresso considers the "core" charge to be calculated or not ?
> >
> >
> >
> >     Atom #   1: total charge =   3.9571, s =  0.9145, p =  3.0426, d =
> > 0.0000,
> >                  spin up      =   1.9786, s =  0.4573, p =  1.5213, d =
> > 0.0000,
> >                  spin down    =   1.9786, s =  0.4573, p =  1.5213, d =
> > 0.0000,
> >                  polarization =   0.0000, s =  0.0000, p =  0.0000, d =
> > 0.0000,
> >      Atom #   2: total charge =   3.9569, s =  0.9154, p =  3.0415, d =
> > 0.0000,
> >                  spin up      =   1.9785, s =  0.4577, p =  1.5208, d =
> > 0.0000,
> >                  spin down    =   1.9785, s =  0.4577, p =  1.5208, d =
> > 0.0000,
> >                  polarization =   0.0000, s =  0.0000, p =  0.0000, d =
> > 0.0000,
> >      Atom #   3: total charge =   3.9554, s =  0.9153, p =  3.0402, d =
> > 0.0000,
> >                  spin up      =   1.9777, s =  0.4576, p =  1.5201, d =
> > 0.0000,
> >                  spin down    =   1.9777, s =  0.4576, p =  1.5201, d =
> > 0.0000,
> >                  polarization =   0.0000, s =  0.0000, p =  0.0000, d =
> > 0.0000,
> >      Atom #   4: total charge =   3.9573, s =  0.9164, p =  3.0408, d =
> > 0.0000,
> >                  spin up      =   1.9786, s =  0.4582, p =  1.5204, d =
> > 0.0000,
> >                  spin down    =   1.9786, s =  0.4582, p =  1.5204, d =
> > 0.0000,
> >                  polarization =   0.0000, s =  0.0000, p =  0.0000, d =
> > 0.0000,
> >      Atom #   5: total charge =   3.9607, s =  0.9155, p =  3.0452, d =
> > 0.0000,
> >                  spin up      =   1.9804, s =  0.4578, p =  1.5226, d =
> > 0.0000,
> >                  spin down    =   1.9804, s =  0.4578, p =  1.5226, d =
> > 0.0000,
> >                  polarization =  -0.0000, s = -0.0000, p = -0.0000, d =
> > 0.0000,
> >      Atom #   6: total charge =   3.9599, s =  0.9146, p =  3.0453, d =
> > 0.0000,
> >                  spin up      =   1.9800, s =  0.4573, p =  1.5227, d =
> > 0.0000,
> >                  spin down    =   1.9800, s =  0.4573, p =  1.5227, d =
> > 0.0000,
> >                  polarization =  -0.0000, s = -0.0000, p = -0.0000, d =
> > 0.0000,
> >      Atom #   7: total charge =   3.9600, s =  0.9148, p =  3.0452, d =
> > 0.0000,
> >                  spin up      =   1.9800, s =  0.4574, p =  1.5226, d =
> > 0.0000,
> >                  spin down    =   1.9800, s =  0.4574, p =  1.5226, d =
> > 0.0000,
> >                  polarization =  -0.0000, s = -0.0000, p = -0.0000, d =
> > 0.0000,
> >
> > --
> > Sincerely Yours
> > David G.
> > JCU
> >
> >
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